The 8.9% fee for Neteller is restricted to InstaCash deposits. These are ones that take the money directly from your bank account without waiting the the funds to clear. It's basically a loan, and that's why the fee is so high. If you cash out from Party into Neteller, and then deposit from Neteller into another site, you won't be paying any fees, so don't worry about that.

As a suggestion, you should try whoring the smaller sites' bonuses before attempting to take advantage of the larger ones. With a small bankroll, you can only get a small percentage of the full bonus. For Party, you essentially gave up $75 in bonus money by depositing only $100, instead of $500. There's a post somewhere around here that describes the best method for small bankrolls, but I don't really feel like finding it. Check out the guide on BonusWhores.com for a good approach to collecting bonuses.