I've purchased from Provident several times. They seem to have the best prices on most things when they're available. But service is important to me as well. Their staff is very friendly and goes the extra mile, whether you're spending $50 or $50k. Ships fast too. After placing an order, I usually have it on my doorstep within a couple of days.
And another thing too - they offer some great free resources for learning about different coins. Called 'Buying Guides,' they've helped me pretty easily learn about different coins. See
http://www.providentmetals.com/know...g-guide.html for more