Are pressurised systems pretty expensive?IMO, the best investment you can make for your tank (aside from good lighting) is a pressurized Co2 system. With it, you'll get phenomenal plant growth and coloration. In addition, you'll deal with far less algae. Excel is a great product, but doesn't hold a candle to a pressurized system.
I'd like to go down that route at some point, but depends on the hassle and investment...?