Someone Sounds Off Mic

Without hearing it, it's hard to say whether any improvement can be made or not - but there is one basic rule which applies here; no recording can ever be made more accurate than its original - so whilst you might be able to get rid of some background noise, there are several things you simply can't do - and one of them is to get rid of the 'room tone' that you will have on an off-mic recording. And generally that's what stops it sounding (as you say) 'beefier'.

So you may be able to remove some noise, and you may even be able to EQ it a bit if it's bass-light, but ultimately it's still going to sound 'off-mic' because of the un-removable room tone. You might also be able to improve it with a bit of harmonic enhancement, but as I said, this is pure guesswork because we haven't heard a sample of it. You can't post one directly onto the site, but if you put a sample in Dropbox and post its public link here, that would work...