Just to square on a few things- what power supply did you get?

What CPU and graphics card do you have?

get a SSD...and a hand me down LCD monitor for your second

those are pretty mild temperatures, the only thing to worry about should be theft. Risk of condensation is pretty low but you may want to wait a little bit to power them on.

My goto site is www.slickdeals.net

It's all crowd sourced so deals (many computer deals) get voted up onto the front page from their forum. Check their 'hot deals' forum if you're looking for specific things not listed or do a search in it. Not a good site if you are susceptible to impulse purchases though! :)

Is there a reason that people are setting both cl_interp and cl_interp_ratio?

My understanding is that cl_interp was essentially discontinued, and that you should set cl_interp to 0 so that cl_interp_ratio is consistently used (where cl_interp_ratio "x" roughly translates to the previous cl_interp "x/updaterate")

wow...this is one of the few guys from TF2 actually on my friends list just from mge'ing. I didn't get to know him well but he seemed like a nice humble guy, really sorry to hear of this. I hope his family gets through this, that is awful.

http://www.performance-pcs.com/catalog/index.php?main_page=specials&page=1

One that caught my eye:
quickfire rapid mechanical keyboard (blue switch) $59.95

Also Lots of heatsinks, cases and power supplies a lot cheaper than I've seen elsewhere.

edit: ah looks like some of the good heatsinks/water loops sold out today like the H80. A lot of the corsair ones are no longer listed

to really uninstall and re-install your video driver you should use a program like driver sweeper
http://www.guru3d.com/content_page/guru3d_driver_sweeper.html

you may want to check out laptops on black friday. There's really no reason to spend 200 dollars on a cheap desktop unless you're trying to make a HTPC. Laptop would likely be more convenient to her and she can still set it on her desk and use it like a desktop if she wants. I've seen some early leaks showing laptops for low 200's this black friday that have a lot of battery life.

Wait for black friday in any case. You mentioned wanting to run ubuntu/windows. You should be able to get some really cheap x86 'ultraportables' using baytrail ($200-400), then you could build a full desktop for gaming.
http://www.usatoday.com/story/tech/2013/11/04/netbook-intel-apple-microsoft-dell-lenovo/3433667/

Reviews should start coming out soon on some of the products. Dell venue pro and t100 are early systems available now but I would wait until the rest come out and check out reviews. t100 is really pretty amazing feature wise for the price but i hear the trackpad is awful, lol.

I think you would do well to look at some of the 'baytrail' systems that are coming out (baytrail is intel's new entry level silicon...think of it as a non-sucky atom). 200-400 dollar very portable systems (some can function as 2 in 1's like the asus t100) that run full windows 8.1. Some of them even come with full microsoft office for students for those low price points. The nice thing is all normal windows software would work on it, so if some classes have software programs that need windows you would be able to run them. With a chromebook that would not be the case.

I think the Dell venue comes with a stylus as well that could be good for notetaking...but don't know if it's any good.

You should be getting a 'K' version if going w/ an intel CPU. i5-4670k is best bang for the buck for TF2.

Don't you have components from your current system that are still usable? What hard drives do you have currently?

Personally I can't imagine ever doing a new system build w/o a SSD...it just seems wrong. A SSD is probably the single biggest performance upgrade you can do for typical computer usage. I highly recommend you try to work in at least a 128gb SSD drive into a new build to put your OS and a few games...can't you carry over an old regular hard drive from your previous system for larger storage? In any case I'd spend the money to put an SSD in from the get go, you don't want to have to deal with trying to put your OS on it later.

Source games are highly CPU constrained. The problem with the ultrabook thin form factors is that everything is going to be clocked lower and if it does have a discrete it's going to be pretty low performance...or super expensive. Try to find the cheapest ultrabook with the best CPU if source games are what you're going to play. Integrated graphics should be okay- I would try to get a haswell cpu as that's going to really help the battery life in a notebook/ultrabook over ivy bridge systems...what's your budget?

Are you absolutely set on the ultrathin form factor?

The other option is to get a cheap portable for taking around classes (like a bay trail system) and a bulkier laptop/desktop for gaming.

That is almost a perfectly constructed apology that I'm sure everyone will slurp up, but being 'bored' is about the lamest excuse I've ever heard. At least blame your brother who just happens to have the same voice as you. When a normal person is bored, they stop playing, or go play a different game. Playing in competitive leagues and being a part of the competitive community is a privilege. If you held it in any regard you wouldn't cross that massive line into becoming a cheater and expect to still be able to participate in it. Now that someone took away a privilege from you (i.e. being able to play on a community MGE server) you own up to it but say never again. You only made that alleged decision after determining that the cheats did not fill some void for you. Sure.

If this community has any sense you will be banned from leagues and ostracized, but I doubt it.

I don't know what looks worse, the chair or the carpet. I'm guessing you have dogs? :)

https://www.stanleysteemer.com/residential/carpet-cleaning