> I have seen a 2 Ghz 7447 Single CPU Powerlogix upgrade card on ebay
> a couple of months ago. [...] I wonder how they compare to the 7448 and
> the lower Mhz, bigger cache, faster memory 7455 in real world applications.

For benchmark comparisons between 7455, 7447A and 7448 see posting #37 of this thread:

https://morph.zone/modules/newbb_plus/viewtopic.php?forum=3&topic_id=7638&start=36
(Unfortunately, the recent MorphZone software update broke direct linking to postings.)

Besides, the 7447A has double the L2 cache compared to the 7455 (but no L3 cache). And the memory speed is the same for both.