GPU: is PCI-E X4 worth it?

A bit of info: In the midst of jumping from single core to dual-core (and beyond) I got the cheap-o update-as-you-go friendly ASRock 4CoredDual SATA mobo. My reasoning was that I still had my trusty old X800 (the first lines with higher clock speed) which is AGP 8x, and this mobo would allow to acrue new parts bit by bit. It's coming time to think about finally upgrading the GPU and, naturally, I'm going for a PCI-Ex16 card.

The issue: the 4CoreDual mobo accpets both AGP and PCI-Ex16. BUT the PIC-Ex16 is not a true x16, it's tuned down to 4x.

My question: Would I experience any real performance gains upgrading to a PCI-Ex16 GPU even though it is limited to running at 4x? I run Vista Ultimate and plan on getting a DX-10 card, if that makes any difference.

Thanks guys!

Yeah, that's basically what I thought, but wanted some people with some more experience and knowledge to chime in. I do plan on upgrading my mobo, I was just wondering if it would be noticeable at all if I upgraded the GPU and then got a new mobo. Obviously, it wouldn't be. :)

yoyo, yeah, I know the mobo kind of sucks. I checked the specs and saw the x4 limiter when I bought it, but my plan was to baby-step to better parts. Baby-step with the RAM, baby-steps into SATA, baby-steps into the GPU.

Thanks you all for your advice and help on this!