I recommend the Arizer Extreme Q, you can probably get it used for around that price and its a phenominal vape
Vapolution 2.0. An all glass air and vapor path. One of THE best tasting vapes on the market, regardless of price. At your price point, I think this one's a no-brainer. Here's a 30 page thread on it packed with user reviews and user tips: http://fuckcombustion.com/threads/vapolution-2-0.4940/