>is there anything i should be aware of?

Most major PC manufacturers use non-standard cases; don't bother trying to replace the mobo in a Dell or something like that.

IMO it's worth overdoing the PSU -- you don't pay much more for, eg, a 750 watt model than a 500. I'd suggest at least a 500 watts. It's also worth looking into "80 PLUS" certified models; they're generally quieter, cooler, more efficient, and longer lasting.

For connectors, you probably want the 20+4 main power (normal 20-pin ATX + 4-pin molex). A PCIe power connector can't hurt either. I personally don't worry as much about SATA connectors as 4-pin (IDE hd style) molex -> SATA are cheap and often come with retail packaged hds, psus, or even mobos. Some (older) SATA hds also have both types of connectors.

Most of the components you'll be buying will specify their power requirements and all will specify their connector type(s), so you should be able to determine exactly what kind of PSU you need as the last step of your build/purchase. I can't really recommend a GFX card as I'm not really a pc gamer.

HTH.