The brand is good, but you'll not be needing DDR3 1333 or higher, as Intel processors don't benefit from anything faster than DDR2 800 which would cut your price down to a quarter or something like this. This may change with the upcoming Nehalem, so if you want to re-use your RAM, you can invest that money in the DDR3 1600, otherwise I'd say it's better spent elswhere.
Are they "downwards" compatible, i.e. can I put DDR2 ram in a motherboard that lists DDR3 in it's specs?
No. DDR2 is not compatible with DDR3 motherboards.