Don't worry about the wispy buds. There are still old school growers that use MH all the way through the grow. HPS will give you a quicker flower time, but bud density will be a very little difference. Also, 8 plants will be allot for that space unless you grow SOG meaning you only veg for about a week and then switch to flower. You could use 6 plants PSF in a SOG, and even with that some EXP growers use 8 which is too much IMO, but can be done. Over on another board there is a member that grows 36 plants in a 4x4 area with stellar results.
I have even read Zandor saying that he knows growers that still go MH the whole way. I have 2 1000w MH grotech ballasts and a 1000w digital ballast with a Hortilux mMH and HPS so I can pretty much use what I want except for the fact that I don't have the room to use everything right now. Maybe I will have to actually do a side by side grow with pics and post some day a full MH grow. The reason I don't post pics is because my vision is so bad that my wife would have to do all of the work and with my sight problem she does enough work right now with helping to maintain our babies as it is.

Adieu