Listened to your recordings. Yes, I can hear your PC's fan in the background. You could EQ that out I reckon. Though if I was mixing your voice I'd add cut a bit of the (very) low frequencies - not so much that it affected the actual tone of your voice, I might add - and add a wee bit to the high and high-mid freqencies. And in the process that might emphasize the fan noise.

Can't hear any rumble, but I'm listening on quite basic headphones which might not be very revealing.

If you don't mind me risking a comment on your artistic practice, you do need to tighten up your pitching a tad.

anyway, when you do get your Zoom H thing or whatever solution you come to, it'd be worth your while getting to grips with Audacity's equalization. A useful trick with mixing recordings is to import a similar (professionally recorded) track. Find a contemporary recording of a male unaccompanied folk voice. You then have some sonic information to guide you as to how your voice ought to be tweaked.