jimmy_LD said:
If my Behringer MX2004 has mic preamps, why would I need to bother getting a mic pre for my condensers?
To reinforce participant's answer, you may (as he said) not need a dedicated mic preamp at all, if you are happy with the way things sound.
The issue is the same as any other piece of gear: what is the quality point with which you can get satisfactory results.
For example, one could ask:
Why would you need a Neumann U47 or
an AKG C12 when you already have an Octava 219?
Why would you use Mogami cable whan you already have Hosa?
Why would you want an LA2A when you already have an Alesis 3630?
Why would you have a song professionally mastered when you have some software that will do the same thing?
Why would you want a Mercedes when you already have a Kia?
The answer is the same to all of the above: the higher quality (and more expensive) options will be most worthwhile when you start to get enough experience and skill to notice you are being limited by the budget solutions. Until that time, enjoy yourself!