The ram on the a2630 is full 32 bit so you should have that in use.
Their might be a small amount of ram on one of your other cards topping you over the 8mb limit therefore causing your slowdown/crashes.
I have 4mb on my a2630 and 4 on my hc+8....and it runs sweet.
As suggested use the accelerator ram and reduce the slower ram on your expansion.
