I recommend the GGTS. You can use 510, 808, 901 and 801 attys/cartos. It also vapes at 3.7, 6, and 7.4 volts, whichever you prefer. It might cost a little more than you want to spend, but in the long run it's worth it.
$200 compared to $80ish you call a little more then you want to spend? I will admit that it is a great quality PV but no worth the price in this new market with so many competitively priced devices out there.
If you are just talking quality, you probably can't go wrong with any of the 6v mentioned here. If you are looking for a combination of quality plus price, it's a Chuck.whose got the best 6v for the money(usa)?