When you wire an amp into 2 ohms, you're not TECHNICALLY getting more watts, you're just lowering the resistence, so it increases the current and more power is given to the speaker. The problem with lowering the resistence is THD (distortion). The resistence on an amp works much like a water filter, the thicker the filter (more ohms, higher resistence), the more pure the water coming out will be, but the output will be significantly less (itll take more time for the water to come through) If the filter is thinner (lower resistence), it will be faster, but it might not get all the impurities out. If you look at amp specs, it will give you a THD level at 4 ohms and at 2 ohms...the THD at 4 ohms is usually MUCH lower than at 2 ohms, so to answer your question, the amount of power would be the same, but if you got the 1200.1 and wired it at 4 ohms, you'd get a bit cleaner signal than if you ran the 600.1 at 2 ohms, but with the price difference, most would go with the 600.1 because it isn't going to be too noticeable...
Keep it loud!
JELLYDIME