I have the Odyssea 24" Adv. plus metal halide + 4t5ho, and I bought a used icecap ballast for $80 and sold the odyssea ballast for $50, and added a Phoenix MH
bulb. I couldnt be happier, and I feel like I've got a pretty good quality light for not much money and it was easier to afford because I put money into it over time, like bought the light then 2 weeks later bought better ballast and sold the odyssea, then bought the phoenix bulb. So spreading the purchases out a little bit helped me.
My next light purchases will be new T5HO bulbs b/c the odyssea bulbs are not the greatest but are definatly good enough to keep your tank growing and looking good until you can upgrade.