NEC displays (170 and whatnot) are great. Samsung 172t is nice too.
As for speakers the best bang for your buck would be the klipsch 5.1 GMX.. as low as $179 for the set (at least on their site)...
If your speakers are digital they'll work. If they're analog (minijack type and not optical), then you'll want a PCI card (
www.m-audio.com) that can handle the old fashioned minijack 4.1,5.1, etc.
If you simply have 2 speakers or 2 speakers and a sub you can just use the normal speaker/headphone output ports on the g5
