Scrap the t8's and go with t5's. 6 bulbs would do with t5's, but I wouldnt really go with the t8s personally, depending on your ballasts you may only need to swap the endcaps and bulbs though which would help $$ wise..... but really going to leds wouldnt be a ton more (ok maybe double) for a set up that size if u can DIY.
Also, you could initially start with a smaller led set up, and suppliment it with 2-4 of the t8s (although again the t5's would be a better choice IMO), until you can save up the $$ to do more leds (again if you are able to DIY it this scenario would be alot easier for sure).
The actual light requirements do vary though on the types of coral your looking to be able to keep, and for some things, especially softies, and probably most lps
your lights would be ok.... not ideal, but ok. SPS
would have to be in the top 1/2- 3/4 of the tank and don't expect to see much if any growth, but you would probably be able to keep it alive atleast..... also either way switching to T5s of LEDs, you will want to move all your coral down or acclimate (by diffusing the light, and/or slowly increasing the lenght of time your lights run for) your corals to the new light so u don't bleach or even kill them with such a big change in light and intensity!