make sure you have Rev6 060 if you want to go to 75-80 else I was running a Rev1 for years at 66 with no issues at all.
Believe it or not but the phase 5 accelerators came with better software support, including CyberPatcher to patch missing 060 functions, and in general from what I found (I've owned all of them) has a slightly higher compatibility level than the Quikpak 060 - for example, with Shapeshifter the phase 5 board works better.
The Quikpak 060 is a good board, it came in two versions, a tower version and a desktop version. The desktop version also had optional SCSI with the same connector as the phase-5 CS PPC or MK-3. They are very rare though, especially the ones with SCSI. The version I owned unfortunately had no SCSI, but I know of one user who did have SCSI on his desktop Quikpak 060 board. And yes, the desktop Quikpak 060 board (the "XP" version) does work in the A4000T, and actually shipped in later Quikpak A4000T's as the default 060 card.
Overall you can't go wrong with either, but all things being equal I'd opt for a MK-3 or CS PPC. You can also add a graphics card directly to a MK-3 or CS PPC (The CybervisionPPC) or you can add the GREX PCI expansion board, which is the fastest PCI solution for classics by far - because of the direct connection to the MK-3 or CS PPC.
