According to that site I'd need less than 330w for the kind of system I'm looking at. And that's if I leave a big margin spare, I could get away with as low as 250w if I really wanted to push my luck (which admittedly I don't).

My only issue with PSU's that small is that many seem to be non-modular. Hopefully I can find a good one that is at least semi-modular otherwise my idea of working in a smaller case will be made harder.

Because I bought a 650 Ti right before they started coming out, and while the 750 Ti is quite a bit faster, it doesn't necessarily justify a second purchase so soon when my card is covering my needs fairly well.

That and there are strong odds I may lose my job tomorrow (which has been known about for a very long time) so big purchases and all of that.

Have you built a mini-ITX (or micro-ATX, or similar) before? Because if not, "harder" is going to be pretty well assured. Unlike building in a more "normal" sized case, you are going to have to stick to a fairly rigid build order. This is a great mini ITX case, for example, and one that I used for my SFF build. Just know that it'll be a new experience for you, building in such confines - and that CM case even was laid-out to allow for larger GPUs, so it's a touch more spacious than other mini-ITX.

The point that I failed to make there is that you should be more worried about your power supply's efficiency and fan size (yeah, size matters) than modularity, when building in a tiny case, because no matter what you think is going to happen, you're going to have the motherboard out on the floor in front of you, and you'll be piecing things together carefully and with low tolerances, so you'll have time and space to wrap your cables. Get something like this with a variable-speed, 120mm fan if you can, because the RPM difference between an 80 and a 120 makes for significant decibels.

EDIT: Just saw and [url=http://hexus.net/tech/news/graphics/71201-rumours-suggest-nvidia-gtx-880-870-arrive-q4-year/]this which refer back to my recommendation from my first post in this thread; rough timelines for the 800-series GPUs suggest Q4 this year, so if you're going to be waiting a little a few months to save up for the new computer, you may be building just at the right time to get the big brother of the 750Ti.

Customers are pissed off at Galaxy for not having a low-profile bracket for it. Low-profile with a full-size bracket isn't much good unless metal-bending on an in-warranty card is in your comfort zone.

While it's true that the 750Ti has less absolute power consumption overall than a lot of cards, it's not like AMD cards are power-hogs other than the top tier R9 290/R9 290Xes.

The mid-range Pitcairn Radeon cards (7850, 7870, R7 265, R9 270, R9 270X) are also known for being pretty power-efficient, and deliver high performance per watt:

http://www.tomshardware.com/reviews/geforce-gtx-750-ti-review,3750-14.html

Edit: Oh correction, the top graph is absolute performance, and the bottom graph is PPW, which is a lot less efficient than 750Ti. Still, when Pitcairn hit (it is a 2 year old technology now), it was lauded for its efficiency. I guess the real next generation (of which the 750Ti is the first wave) will be something else.

The 750/750Ti is only halfway to the next generation: new design, current technology. The true next generation (20nm technology) should see an improvement in performance per watt by a factor of 2 or better.

AMD has no next generation of GPUs at this point. Their only announced product is a hybrid ARM/x86 APU.