I use
Knife Center on a regular basis for knife purchases in line with what you're looking for in a knife. I've had very good interactions with them and have probably made a dozen purchases over the past few years; never had an issue. Their prices are usually very competitive with other sites and they've got a good selection of many well regarded brands.
As for specific knives, I'm a big SOG fan, but find myself with a CRKT in my pocket more often than not. I tend to be tough on my pocket knives and the CRKTs (for the most part) offer a nice balance of value and quality. I know there are 'better' brands out there and I have a few of them too, but the SOGs and CRKTs offer what I need at a price that doesn't make me weep. My current folder has been in my pocket for about 4 years now; gotta be a new record. I've tried to replace it a few times with knives from Benchmade, Kershaw, Spyderco, etc, but haven't found one that does as well for as little paid. Fine knives to be sure, but I don't need 'fine' in my pocket. I need something that works and won't cause me undue stress if it gets lost or broke in the process. SOG and CRKT both meet the reliable standard for me and the price standard for my wallet. :D