I don't know anything about aquascape, but while googling, I see lots of negative comments about no replacement parts or support. However, I also found the following: I have the SFA4500 too and they are pretty simple to rebuild if you are
mechanically inclined. Mechanical seals are available from Bergman
Speciality in Jackson, MI for $87.50 and the bearings can be picked up
at a local bearing supply for about $15.00. For $100 and about 2 hours
of time your pump will be as good as new.

You might want to check Bergman out, but it is still expensive and I suppose might not work, depending how handy you are.

A 3000 gph pump is large but not necessarily over sized. A 2000 gph or less might be better. However, as you have probably noticed, you can get by with nothing, so .....
If you go for a new pump, I suggest that you find a mag drive unit for the low energy use. I have a 2400 gph Laguna Pump that is running well continuously in its eighth year, but there are probably plenty of other pumps that will do as well.

go to the two drs. and look at the fish mate pumps,the 2300 uses 85 watts of power.they are the most energy efficient pumps