Wow! Yeah, I'd say you overdid it. Normally, a 3/4 hp pump is all you need for an 18x33 oval--and even THAT is usually up-rated at 3/4hp, not full-rated. I'm not sure what the lo-speed HP would be but I would guess it might be in the 1/2 to 3/4 hp range, in which case you would NEVER run your pump on high, probably not even for vacuuming. I'm guessing that 2 speeds generally run at 20% of their full speed power when on low. It will save you scads of electric to run on low, too.

Of course, if, at some point you need to dump half your water to refill, the full speed will pump the water down really fast....unless you only have a skimmer and no low drain.

Carl