Motherboard & RAM comp. question

I'm thinking of buying a system with a ASRock ALiveXFire-eSATA2 R3 AM2 / AM3 ready MoBo, but when checking it out on

http://www.asrock.com/mb/overview. [...] R3.0&s=AM2

I found two possible problems:

I want to install 8GB (4x2GB) PC2-6400 800Mhz DDR2 (Kingston) on it, however the specs tell me that "**Due to the chipset limitation, if you adopt 4GB or more memory, the actual memory size may be less than the installed memory size." Does anyone have experience with this combo, will there be a problem?

My CPU will be AMD Athlon II Quad-Core X4 QC 620 240 4x2.6GHz Socket AM3 2MB, the specs tell me that "If you use AM3 / AM2+ CPU on AM2 chipset motherboard, the system bus speed will downgrade from HT3.0 (5200 MT/s) to HT1.0 (2000 MT/s), but the CPU frequency will not be influenced." I don't know what this means exactly, will my total speed go down?

Thanx a bunch for reading, hope someone can help me out.

For memory, that refers to windows 32 bit systems not recognizing more than 3.25 gb. For the second reference, that refers to "hypertransport" which I view as a marketing gimmick, more or less. Yes your speed may drop, but you won't notice it with the other limiting factors of hardrive, chipset, etc. If you want top performance, get a board with a southbridge 710 or 750 chipset. This board has an older 600 chipset.

Or will the Athlon 2 Quad-core 620 support a 64 bit system?