I've been trying to get a good AGP card to go in to my HTPC for a while now to replace my 6600GT, especially (mainly) since I've got an HD DVD drive now. The Radeon 2xxx HD AGP series has not been the dream that I thought it would be when I first heard of it after reading all the negative reviews regarding driver issues and fan control. There are only so many options when it comes to AGP, and then there is the issue of the additional price to get an older piece of hardware. So here's my situation. The motherboard I have is an ASRock Dual-VSTA; it has an AGP slot and a PCI-E graphics slot. The drawback is the PCI-E slot is only 4x. When I first got this board there were a limited number of PCI-e cards that would work, but after going to their site today there are a lot more cards compatible now, some of which are the 2600 series pci-e cards (which I haven't really heard any bad things about). Would I be better off to scrap the idea of going to another AGP card and just get a compatible pci-e card? Or should I get the best AGP card I can for this board because of the 8x vs. 4x difference? I read a review before posting this comparing the AGP and PCI-e performance on another motherboard that was similar to mine that had 8x AGP and 4x PCI-e. Although the AGP won in all the tests, it was only by a slight margin, and the review had the performance difference at about 5% between the 2. I don't use the HTPC for gaming, just to watch movies (DVD and HD DVD) and record and watch television. My resolution is set at 1080i. What do you guys think?
8x AGP vs. 4x PCI-E
AGPx8 = PCIe x4
Speed should be able the same but PCIe x16 would be *just* a tad faster. It's not like a 2x00 series card is going to tax a PCIe x16 bus much anyways (a 8800 Ultra hardly uses all of the bandwidth available to it).
But I would highly suggest, with all of the other issues you have, to start over with completely new hardware. I really think that the hardware you are using now is the source of your problems.
I don't have any direct experience with PCI-e x4, but I don't imagine that video processing would tax the interface. Not that much data is traveling to the card.