Double check to be sure that your tank doesn't have a tempered bottom before trying to have it drilled. You can't drill tempered glass. It'd shatter.
I personally think that sumps are fantastic, but you can have an awesome tank without one. I see two benefits off-hand with a sump that affect the health of your tank (there are other benefits as well, like hiding equipment). The first is that you can find a higher quality skimmer for in-sump use than you can for hanging on the tank. The second is that you can do a refugium in the sump. Refugiums are really sweet, but not a requirement. And you can skim a 55 just fine with an AquaC Remora that will hang on the back of your tank. It's not as good as say, a Euro-Reef, but it'll take very good care of you and your tank (and it's more cost-effective).
If what you want is an affordable tank that looks really nice, consider keeping it simple. You need good lighting, a good skimmer (not a Prizm, not a SeaClone, probably not a BakPak which is good but underpowered for this tank), good water motion, and plenty of rock. Those are the big things to consider.