Vinyl newbie - have a few questions

Ok, I'm fairly new to vinyl. I have a few items I'd like some advice on.

My vinyl system is a small collection of hand-me-downs:
MacIntosh Mac1700 receiver
A/D/S L500 2-ways
and the recent addition, Denon DP-52F w/ Ortofon OM-3e

I realy like the over-all sound, and am really impressed with how dynamic instruments are compared to CD. I love how the brushes on drums sound like brushes instead of static like on most CD remasters. However, I have a couple gripes and need some direction in working them out.

I suppose I should mention that a majority of my listening is jazz, mixed with classic rock. Right now my personal collection is probably only 30 discs, but with my father's neglected collection I have three or four hundred within a couple minutes drive from my house.

First of all, is the background noise. I just can't seem to get it completely black behind the music. I must say, it's not much noise, but I notice it; even when other's don't.

Second, on some stereo recordings the mid-range seems a little "compressed" to me. Even my wife has noticed that it just isn't as dynamic in the mids as the rest of the range. However, this seems to only occur on stereo discs, when I play mono's I get a really sweet full-range.

Third, I just need advise on cleaning albums. I'm just using my discwasher from 1980-whatever while hunting through boxes at my dad's for his Zerostat. Any suggestions for cleaning regimens that don't include dropping a thousand dollars for a RCM would be appreciated.

So I guess the crux of my inquiry would be; where am I going to get the most bang for my buck in improvements?

I appreciate any input you can give me.

M