I don't have a kipper2k, Though I would not mind one.
A conventional 8meg Fast ram address space is from 20000 to 9FFFFF. If the Kipper2k 4megs of ram uses the conventional address space there should be no memory addressing problems. Especially since it should be autoconfig space. It is not like you have a bridgeboard or a zorro II graphics card that is taking up autoconfig memory space. As long as you stay under 8megs total you should be ok.
The bigger concern for the ACA500 is that it does not like 68000 socket accelerators. It can be damaged by them. I don't know if the kipper2k would have the same issue or not? I don't expect the kipper2k to effect bus timing etc., but I would check with Jens or Amigakit or someone here at Amiga.org to find out for sure. We don't want you to damage your Amiga.
As for the ACA500, its fastram is mapped to C00000 or what is referred to "slow ram". This was done for game compatibility. some old games expect ram at the C00000 address.
But don't fret. The ACA500's ram even though mapped to "slow ram" is is very fast, Faster than typical 100-120ns fast ram.
I don't know if the ACA500's "slow" fast ram would allow you to get above the 8meg auto configuration space or not. ie 8megs of fast ram some "slow" fast ram. Some of the trapdoor memory expansions "do" allow for this (like the Adram 540, but the some of this ram is not autoconfigurable and needs a patch program to be run to make this happen). But eitherway the configuration you are speaking of is below the 8meg limit anyway.
If you put an ACA500 on an A500+ that only has one meg of chip ram the ACA500 can be configured to make the one meg of its ram become mapped as "chip ram" for of a total of 2 megs of chip ram plus one meg of "slow" fast ram. This is also true for a 1meg Agnus with only 512k of chip ram. 512k of the ACA500 ram can be mapped at chip ram. The ACA500 would be left with 1.5 megs of "slow" fast ram.
If you can get a hold of an ACA500 (I think they are out of production), I would highly recommend it. I have one on my A500+ with one of Jens's A1233, The combination is significantly faster than a stock A3000.
Either way I agree with you I cannot wait for the ACA500plus or the Vampire 500. I expect both to be awesome.