My part orders splits into roughly:
Airsoftparts.ca: ~$710 single orders, + $380 from group orders
A&A Airsoft: ~$800
ASC Armory: ~$600
ASC Buy/Sell: ~$740
Illusion: ~I forget, but VERY fast shipping on emergency parts!
Some other old school retailers, I forget too, sorry guys.
There is a little bit of gear mixed in (going by user account) but for the most part this is all parts sales.
What I look for is:
1. PRICE and Availability - One without the other and I stop shopping there. I need both a good selection of stuff that is beyond just normal repair parts and prices that are competitive. Both Airsoftparts and Redwolf shine here. Now, since Systema parts are very hard to get ahold of, EmpireAirsoft gets kudos for having stuff in stock and ready to ship.
2. SERVICE - For me, service is unfortunately second. I rather get my stuff and for a good price then be lead on for months of polite conversation and excuses for piss poor prices. Airsoftparts has excellent prices and throws great deals we asked, also incredibly polite to deal with and very quick responses. DST (Daves Surplus Tactical) gives great prices IF phoned and not internet ordered. Redwolf can be a really service #@$ sometimes but have excellent selection and prices. A&A has great service and Mark will actually pay attention to well worded corrections (fixed an error on a battery charger description, that is service to everyone).
3.In Canada: Meh, I don't mind waiting most of the time for stuff. Huang, Empire, and Redwolf demonstrate this. Mind you, I have had emergency repairs to do and being in country, and in-stock has really paid off. Mind you, that is for boring repair parts. I don't pay more usually for something in-country if I can get it overseas for way less.
Final words: You will have some very stiff competition here starting out. Huang and Airsoftparts, between the two, have really made it easy to shop in-country. For large orders of stuff, Redwolf. For my PTW stuff, Empire. The only market I can see for you to dominate in is bringing in restricted stuff, but we all know how those threads go...