mate ditch the halogen, there no good for growing! youll get poor veg growth and next to nothing budwise. get some cfls if you must but the halogen bulb will do little other than create heat and nothing much useful to the plant!
4x5 ft is big enough dude! and even a few more plants. you need some fresh air being pumped in and the same back out, and a fan on the little beauties to keep the circulation and for the stems to grow a bit of resistance! will help further down the line to hold them buds up ;)