As was discussed
earlier unfortunately angled SATA cables aren't really an option with my board for other than the ports at each end (otherwise they just block the adjacent ports) and zyrobs found (with another board) that they still push the card out a bit, and I'll want it to be in securely considering the weight
I expect the angled cables would clash with any card long enough to reach them, not just the Accelero Xtreme.
Yeah, PCI-E speed is locked to 100Mhz and Biostar have confirmed this board is a POS anyway "when system resume, it will check many places include voltage and clock, also bios have problem to program the OC frequency and voltage after resume, please don't use standby while OC it might cause problem".
The only thing I haven't tried is setting the voltages in BIOS but putting the FSB back to 200 and using AMD Overdrive to increase the FSB from within Windows. I'm not confident this will work very well though and I think I've read about AMDOD "forgetting" the overclock (maybe after resuming). It might not work well with PhenomMSRTweaker either, which I want to use to save power/heat when idle.
Thanks for the Rebels Haven link but I saw that already when I was looking into this problem, and that seems to be yet another problem with the TA790GXBE with ACC enabled, which I'm not using.
Unfortunately that other site doesn't appear to have "right-angled SATA ports that won't block my long graphics card" as a searchable option, so the only way for me to find a board is to look at lots of pictures

It doesn't let me filter by boards with 7+2 audio (multistreaming) either, but these seem to rather hard to find now, which is a shame.
The Asrock
890GX Pro3 looks like a contender, as the right-angled SATA ports look low enough down the board to avoid any 3-slot card/cooler. I also like that the DDR3 slots are a bit further away from the CPU socket than usual, which means less chance of the RAM clashing with the fan on my TRUE rev. C (one bonus of getting a new motherboard is I can get 8GB DDR3 for £50-60, which I'll probably get back selling my 4GB Corsair Dominator DDR2).