IMMO, These are the best Company's to go with. G&G, G&P, KWA, LCT, and KA.
But, what is you exact price range you are looking into?
If your starting out with a small budget, go with an Echo 1.
If you have a mid budget meaning 250-350. Go with G&G or LCT.
If you have a higher budget 400+ KWA, KA, and G&P are the way to go.