I'd say it depends on the space you're trying to fill...

400w hps has a footprint of about 3ft x 3ft, and it might get a little cramped for 8 plants. This of course depends on how long you veg them for and how big the plants get in flowering.

There are plenty of success stories using CFL's and T5's for veg, but you will need a lot of them. Again, depending on how long you are vegin for.

If you have a switchable ballast, get a 400w MH bulb for veg. Even a 250w would be enough for veg (might need to get the right ballast though). Then get a 600w or 1000w HPS for flowering and you're golden :thumbsup: