the 3700 has little advantage over the 3200.and your pc2700 memory is slow you should get pc3200 if you go socket 939.get a 1 GB kit (2 x 512)or bigger from a name brand like Corsair,OCZ,Cruical,Kingston
heres some AM2 ideas
MB
http://www.newegg.com/Product/Product.asp?Item=N82E16813130050
http://www.newegg.com/Product/Product.asp?Item=N82E16813131022
CPU
http://www.newegg.com/Product/Product.asp?Item=N82E16819103032
http://www.newegg.com/Product/Product.asp?Item=N82E16819103637
MEMORY
http://www.newegg.com/Product/Product.asp?Item=N82E16820227126
http://www.newegg.com/Product/Product.asp?Item=N82E16820145566
as far as power supply im running a 420w(cheapo raidmax $20.00) with no problems
my specs
Amd 3200 64 939
Epox 9npa + ultra(it was cheap)
Corsair value select 1 gb kit
Evga 7600 gt
Audigy 2 zs soundcard
2 HDD
2 optical drives
2 120mm fans