I need a 4x agp for an old shuttle pc

for a quiet card get a 4650, for raw power get the 3850, it will put out signicantly more heat than the 4650.

Most agp cards work in 4x or 8x mode but look for some thing low power like a 4650 agp.

Does performance matter? If it does, then pick up the 4670 AGP. It's an AGP 8x part with 512 or 1GB RAM. They're running $110-$140 on Newegg right now, and some provide newer interfaces like HDMI and DisplayPort. If performance does not matter, then I would hit up eBay or a local shop for something cheaper. Odds are good you can find an old cheap machine w/an AGP card (or maybe just a card) on craigslist locally for pretty cheap.

P.S. - 4670 AGP will require a 4-pin molex connector and an additional 75 Watts of juice to run. As far as I can tell, the 4650 won't but won't be as fast either.

Hope this helps!