I don't agree. Not with a V3 anyway.
A PCI Voodoo 3 is only fractionally slower than an AGP one. This difference can be made up for, in the fact that the PCI card can be moved to any slot you want. This means, you can move it to the bottom of your case, in the cool air. This also means that your CPU won't have blocked off airflow from the video card.
Essentially, this means BOTH the video card, and the CPU will run cooler. And if you overclock, you will get back that tiny speed loss back, and then some.
Anyway, to get back to you, badwazoo, don't take that card back. Even if you don't take my advice on the whole PCI card positioning thing, the speed loss from the PCI card is so small, it's not worth the effort of taking the card back.
------------------
PII 266 @ 448, 64MB of 66MHz SDRAM @ 79, Aopen AX63 Pro, V3 2000 @ 175, 13.6GB - 7200rpm WD Expert, SB Live Value, LG 40x CDROM, Jazz 300W Front Speakers + Sony SRS PC300D Rear Speakers / Sub Woofer, 15" Monitor, Full Tower Case, Win98 Original Edition.