So in reality the accelerator wont add, or deduct a whole lot from the WHDload experience, but the memory is needed, and "some" games, like Frontier Elite II gladly use all the CPU power you can bring it... From the start i'll probably mostly play K240, but Frontier IS on the list as one of the most played games on the Amiga, making it a slightly less choppy experience would probably prolong the usage.
The addition of a MMU does nothing, or next to nothing, and isn't worth taking in to account.
Guys, thanks a lot, you've been helpful. I'm going to shoot for a faster card, probably the /42 flavor, and hope that it provides me with all the CPU power i'll ever need. It's still a dirt cheap upgrade.
A big thank you to all of you.