So I need lighting, I do not want to use the 400 watt MH that I have. I have seen multiple units for sale ranging from a 6 bulb T5, 4 bulb T5, 2 150w MH with 2 PC actinic, 1 250 with 2 PC actinic. I am really leaning towards T5 over MH mostly because if I were to do MH I would want the 2 150s and the cost of bulb replacement on that would be more than the fixture would cost! So let's see some suggestions, there is a couple great deals out there on both 4 and 6 bulb fixtures, I have a ballast as well so I could get a four and then add two into the canopy as well...

This would be for a 36in tank.

how deep? or width for that matter. If mh is your choice I would go with led actinic over the pc's IMO
Also what coral are you keeping or plan on keeping.

Tank is 36Lx18Wx21T

Most fixtures only use T5 or PC actinic, using LED atinic with MH would be a hassle since LED's really don't need to get more than warm and with MH it's gonna get hot.

I've run my 12 3w led's next to my 2 175mh for six months with no issue but I may be the exception.