Hello G'day,
The memory limitation is more a question of chipset used; my Aus P5Q does support 16GB of memory, while your P5B like yours is limited to 8Gb (both MB support Quad core but have different chipset).
The idea is to find the processor we want to use and a motherboard that will support the max memory we're looking for. For Quad proc, there are many boards available that can use 16Gb of memory. The memory you will use will be dictated by the kind supported by the MB (ecc, non ecc, buffered, un-buffered etc).
Once again, my P5Q is using UN-Buffered, 16Gb of it and never had any problem.
Now, the i7 (I less familiar with it and didn't study it much yet), the main problem is the cost of memory; while you can get an affordable system with 12GB jumping to 16GB or 24GB (depends on the processor i7-i5 and MB) you will pay up to $2500 EXTRA just for the memory!!!! So i7 are right now interesting up to 12GB of memory, over that, well, you're better have a lot of $$$ available. Eventually memory price for the i7 will drop, but right now it is ridiculous.
For a Quad/16 or i7/12Gb you will probably pay between $1000 and $1500 and maybe less.
With Hw 3.3 and the Metz even a 8GB computer will load the Metz at 8Gb. I don't know with Core2 you have, but if I were you I would probably buy more memory (to go to 8Gb), W7/64 and the Metz.... I'm pretty sure that it work great. Even better, since yo already have 4Gb, just buy the Metz (loads @16 bits with /3gb) and play a while that way to make sure that your proc can handle it, then if it does, buy another 4 gb and W7... you will save a lot of $$$ and eventually, once memory price have dropped, go for a new i7 and 24GB...
Don't forget V3.3 gave a second life to your proc.
Hope this help a bit
Regards
François