An A1200 tower system is actually more expandable than an A4000. The accelerator cards are more common and you can get a Mediator busboard to plug a pc-style graphics card and sound card into it. Just make sure that they are supported by the available drivers.
For AHI (sound drivers) you can see what drivers are available at
the AHI website. And for either Picasso96 or CyberGraphics (graphics card drivers) the safest bet would be some sort of old Voodoo PCI graphics card.
If you decide to go with the A4000, then be sure to check out the
CyberVision 64-3D graphics cards. And try to find a Warp-Engine CPU daughterboard (They trim 80% of the propogation delay from between the CPU and memory by putting the CPU and RAM on the same card.)
As for memory, the A4000 takes fast-page SIMMs and won't work with EDO SIMMs. A Blizzard accelerator on the A1200 will take either type of memory. I've got 16megs of 60 nanosecond EDO in my 1230 Blizzard (68030-based). It's enough for most tasks except the latest version of Total Chaos takes 32 megs fast and an '030+ is recommended for that.
As for Total Chaos, it's slowly becoming more portable to non-AGA systems so you may be able to get by with a non-AGA Amiga such as a newer PowerPC-based system eventually. ;-)
