DDR2 667 vs DDR2 800

can you see the difference in terms of performance say, gaming?

Most likely not, but if you are going to be buying new DDR2 ram, spend a bit more and get the faster DDR2 800.

If you were going from high latency DDR667 to low latency DDR800 then you might see some difference otherwise I would expect any difference to only be noticable in benchmarks. Still, unless the DDR667 is much cheaper than the DDR800 I would go with the 800.

no not to much of a noticible difference