At 6', IMHO, you don't need gear, you need more work in the gym. I never touched the stuff until (at 6'2" 223#) that point. You can add another 20# gear free very easily, so I'd not look for a quick fix, but more for a solid training, eating and sleeping regimen.
BTW, how old are you? You mentioned 6' and 170#, what's your BF as well? Sounds very low or you're just not developed yet.
Diet:
Should consist of at least 3000 calories a day (to add mass) for your size
Sleep:
Are you getting at least 8 hours?
Alcohol:
do a search, this should be banned from your diet while bulking...it short circuits your gains
Training:
What's your current routine look like? My first 2 years, I was 4-6 days in the gym, diet was about 2600 calories, and I was coming down from being a fat fuck of 296# to my picture (in the signature) at 218# and 8% at 6'2".....you can get to at least 190-200 without gear....make those gains first, then reevaluate....gear is not a quick fix, nor the first answer, IMHO.
bo