It's up to you but the aggravation of something going wrong might offset any savings from sales tax.
Having built dozens of PC's I've conclusion that price isn't everything, particularly as it relates to memory working on different motherboards. I urge you to buy the motherboard, cpu, and memory from a single supplier so no one points figures at each other if there's an issue.
While a few have had problems with newegg, most swear by them if there are issues (i.e. their RMA process is pretty hassle free).
However, if you still need the absolute lowest price (and are not near a Fry's where you can take advantage of their frequent MB / CPU / memory sales), use
www.pricewatch.com to find the lowest prices. However, make sure you also use
www.resellerratings.com and check the feedback.
Anyway, it looks like you are looking to spend
Charlie
P.S. It helps that I have a resale account with Newegg

And I have to charge sales tax to someone in CA that I build a system for whether the parts came from out of state or in state. Newegg has both great prices and great service.