Have you taken a look at InsideSun or Maryland Hydroponics? Both are great companies with deals on cheap lights. If you really want to make an investment you're going to drop more coin but if you are satisfied with a budget unit and reflector I'd just get a new 400W HPS. You're probably going to spend just as much on high-output CFLs as they are trendy right now.

You can certainly grow without a HID, though. The heat output from CFLs is greater than equal wattage HIDs and they may end up being as expensive or even more expensive. It's probably also a slightly slower growing process with smaller flowers due to less efficient penetration and a far smaller high-lumen output field.

Either one is going to produce quality flowers once dialed-in but I think the better option is the HPS. Happy growing!