If this is your 2nd go-round, you should have an idea what to expect.
At 21, have you had a blood panel done ? Just so you have an idea where your at nat. ? If your cranking out 400 free test on your own, why shut down your system for 500 ?
Depending on your results and your size (taking into account bf%), I'd be doing around 750mg wk Sust. and 200-400mg wk either Deca or EQ. You could front load with some d-bols or better yet some prop for the first couple of weeks if you felt the need. Run it for around 16wks, drop the Deca in wk. 13 or 14. Wait a couple of wks after your last pin and start Nolva/clomid for 4 to 6wks. At your age your nuts should pick back up quickly but if you or your GF don't like the raisins (atrophy), you could run HCG at around 250-300iu's 2x per wk to keep the boys hangin' low. Maybe keep some arimidex around in case of boobies.
If your diet and training are in order, you'll blow-up nicely...