I just cashed a larger than usual paycheck & am also looking for the best deal on a PSP. What's weird is I can only find the "Core" package & they're going for $169.99 absalutely everywhere. The only place I've found giving any kind of incentive is Circuit City. They're giving an extra rechargable battery; which looks like an official Sony PSP battery. They say it normally sells for over $30.
Dell.com sells a few systems, including the PSP. The good news is they don't charge shipping/handling & they're .99 cents cheaper than the stores. Then again, if I'm paying out that much cash then I'd rather just go to a store & have it in my hot little hands immediately.
It looks like Ebay is the only option for finding a PSP for less, but then there is the "burn factor". I just got burned by a seller. I bought a used PSP w/ accessories as well as a new DSLite. They never arrived, I filed a complaint, & now he's "no longer a registered user". At least I payed through PayPal & will get my cash back eventually. Still, it really pissed me off.