SVDayton.
Sorry about that......I missed the post from the 16th. I would recommend going with the IB4200s. But don't waste the extra $$ on buying matched cells. Ryan, pretty knowledgeable about this stuff, recommended a while back that after a handful or two of runs, they won't be matched anymore. Balancing/form charging once a month will get them back a little, but that's as far as keeping them balanced will go.
If you can't get the IB4200s, then go with the 4500s. I run the ELITE4500s and they take quite alot of abuse, even when I run my largest prop (CF48).