Improving recording quality of the Zoom H5. Extra microphones?

Hello everyone,

I have a Zoom H5 which I use for casual recordings of rehearsals and gigs and I think the sound quality is usually pretty decent. However, the H5 also has two XLR inputs and I´m toying with the idea of buying two extra microphones in an attempt to improve the recording quality. I don´t intend to spend too much since this is only a hobby project, but have been considering cheapish condenser mics (the H5 can provide phantom power) such as the AKG C1000 (seems practical since it can also run on on batteries) or AKG P170. Anyway, I guess my questions are:

1. Would the C1000/P170 be suitable for this kind of recording? If not, are there any better contenders in the same price bracket?
2. Would there be a significant improvement in sound quality as compared to the built-in Zoom mics, or would I have to spend (much) more?
3. I also have a spare Shure Beta 57. Would that be suitable? In that case I guess I would be better off just buying one more of those.

Thanks in advance!

/Saxray