What HPS should I buy for My Tent???

I have a Secret Jardin DR60 currently with 125w fluorescent growing some clones. I want to buy a HPS system to use for flowering in the following weeks. Shoud I buy a 150w, 250w or 400w. Currently i'm looking at this 250w setup because it will fit.
http://sunlightsupply.com/hort/products.aspx?request=SUN-SYSTEM-2-ENCLOSED-BALLAST&title=Complete Systems&type=product

My tent is 2 by 2 and about 5.5 feet tall will a 250w be to Hot?? or should I go with the 150w?? Any help would be great!

From a website that sells your tent:

"Use the DarkRoom DR60 for holding a mother plant or growing a small number of plants. A 2' x 2' plant tray fits perfectly. Ideal for either a 2-foot T-5 HO Fluorescent or a 250W to 400W HID light system. "

I'd go with the 400W. Inside Sun sells them for $90 bucks. I bought a 400W from them and it works great. I would buy it from their e-bay account though.

I'd go with the 400 as well. I've got a metal 30"x30" cab with vent fan. Attached are some of the results.

Go with the 400, because you can always expand your grow space. A 250 is 'ok' for hobby growing, but if you want to grow dense buds that look like the shit in High Times, you need the penetrating power that 400,600,1000 watters provide.

The drawback is the heat. You can't monkey around with a 400, they need to be properly ventilated, otherwise your temps soar into the 90s and make your shit unhealthy. Pretty much have to use air cooled hoods(reflectors) and high powered centrefuge fans to do the cooling. Higher cost, more work, better bud.