if you have the ability to rent a decent mic pre I would say try that first.
A good pre/channel strip can make all the difference, but the Achilles heel will be your interfaces converters.
So you could have the best mic pre in the world, but if the A/D conversion is compromised, then your not getting more quality, your just bogging the great preamp signal down with weak converters = weak audio.
I recently had the chance to use a UA LA610 channel strip and it made a HUGE difference in quality to my recordings so to sum up my point:
Yes mic pres make a difference, but not without a good A/D conversion (high quality interface).
Also, the room you record in with a condenser mic plays about 85% on the tone, as the mic is simply sampling the air pressure changes and sending the electric impulses to your interface. Whatever reflections are bouncing around the room/mic can cause phasing/shitty sound output. Sound dampening/proper room treatment does wonders for a good condenser mic recording.