I think you need to decide further what you're going to keep. Softies can inhibit SPS growth, so you might not want SPS. In which case you can get away with less. But, you may want SPS and decide later that you really love it more than life itself, and then you need more, and you don't want to end up not having enough light available. How about clams? They like to sit on the bottom. so lots of light.
Most LPS and softies can take a lot of light, so figure out the most demanding thing, buy lighting for that, then you don't have to upgrade.
Then you can figure out MH/LED/T5/Solar flares and what works best for your setup and wallet.
