I have a 50 gallon corner tank, it's about 36" corner to corner, I'm using 2 6025s plus a 500gph return pump. My tank is primarily SPS and the flow is just about right. Still wondering how different the 6045s would be. The ideal solution, unfortunately, would be two 6055s and a controller, but that's big bucks for flow in a small tank.
If money is an issue (it usually is...) I would suggest trying the 6025s first. I'm sure you could sell them for close to what you paid if you realized that you want more flow. I wish I could describe the flow in my tank better, but I'll say that there's pretty good water movement in the entire tank, and only a couple of spots where I can't put corals due to the fast unidirectional flow. There are some spots in the tank where the flow could be stronger for the corals, but I also have 4 clams and I need some calm areas for those. Of course your rock work really affects how the flow travels, so each tank is different. I bet there's not much difference between the 6045s and 6025s in terms of really noticable flow, but maybe I'll take that back when/if I try some 6045s in there.