Sounds like you're already using decent hardware. What's wrong with it? It's not too old right? Keep your stuff in warranty or close, if you don't want to feel too concerned (not everyone shares my opinion on this).
If you have stuff setup to be redundant and good backups, you're doing pretty good. One server = single point of failure, no matter how good it is, that would make me uncomfortable. There's a lot you can do on a budget by making smart decisions around how stuff is implemented software/hardware/infrastructure/support wise.
If you don't have precautions/things in place, maybe you should be worried. If one system dies, are it's services are gone? How will that effect business? How fast can you recover?
Pitfalls? Depends. You didn't provide too much info. Cheap drives can fail or be slow. Cheap cases can overheat. Cheap fans can fail. Cheap SATA/SAS/RAID controllers can screw up or not perform as expected. Cheap power supplies can die or if not redundant, leave you without power. Motherboards can do wonky things. Systems without remote consoles (ILO, etc...) can be a pain to manage. Cheap network cards can have cheap drivers or screw up. Lots of little unforeseen issues can occur. On the other hand, you can get cheap as hell entry level stuff that performs amazingly. And more expensive stuff can be wonky sometimes too.
I've seen it all, in decent* server grade, lower end server, workstation and consumer grade equipment. Higher end stuff seems to do better in the long run (way past warranty). But if you can't afford it? Or you can only afford one server and can't implement proper redundancy?
There's nothing essentially wrong with dual servers running with Xeon's, ECC memory and RAID. Unless you have a problem with it.