I would probably just continue to use the 1 hp you already have. When I was looking for a 3/4 hp pump I was told the same thing by the pool store and they tried to sell me a 2 hp for my 200 lb sand filter. I ended up just ordering a 3/4 hp pump online and had no problems with doing that. Since I went from a 1.5 hp to a 3/4 I have noticed it filters better and my suction side barracuda ranger vacuum works much better too (it got stuck alot) it doesn't get stuck any more.

Hope this helps!!