Mwave is a good source. I've used it for my clients for years, along with Newegg.
However, if you're planning on using the motherboard 'Combo' deals, verify the combo price against individual pricing at other sites, such as Newegg. I'm getting ready to build a new system for myself, and found that I got a better overall price buying the individual components at Newegg then using the combo deal at Mwave. The Combo deal at Mwave was the same as ordering the individual componets from Mwave. There was no savings at all. Newegg gave a better deal, buying the same components separately from them. The only component that was $4.00 more at Newegg was the motherboard. The pricing was better at Newegg and most of the components also had FREE shipping.
As for a motherboard, I'd recommend the Asus P5Q-E. It's got good reviews for a mid-priced MTB. I also just put one in another Aces High player's system. It's a sweet MTB in my opinion. That's what I'm planning on going with, along with the Q9550 Intel Quad CPU, Kingston HyperX 2GB memory, BFG GeForce 9800 GTX, and the BFG ES-800 P/S, (as soon as I verify whether they've fixed the problems that have been reported with that unit).
I'm using my current case, DVD writer, etc, etc, but the cost will still be close to $800.00.
If yer looking to save money, get the Asus P5Q-E, and then pick a cheaper CPU like the Q6700 or the Q6600, (check reviews to see which one appeals to you), and instead of the High speed memory, use the regular memory until you can afford better. That will get you into the ball park. If yer already using PCI-E, then you can also save by using your existing Video Card. Using your existing Video card will also keep you from having to buy a new P/S also.
Wabb