8.5 studio/Tascam US-1641 interface

Hi pal,
I'm similar, a drummer using a Tascam US-1800 to record my band's rehearsals.
The rule of thumb here is to have your Tascam's channel levels set so that they are as high as possible without going into the red. At this point the fader levels within Sonar do not have any effect, so you can set up a template with the levels mixed at the approximate levels you would want to play back at, so that when you come to mix you only have a bit of tweaking to do.
Recording a lot of tracks at once it's best to record without too many effects and add them when mixing.
How to get rid of that garage sound? This is where it starts to get difficult/expensive, as you won't get a killer sound with cheap mic's.
You can get the sound better by experimenting with the placing of the mic's around the kit, but there is really no substitute for really good mic's.
Other than that, keep reading, have a look at the tutorial videos and keep playing.

put noisegates on the toms. the crosstalk is what is causing the "garage sound".
Then eq the kickdrum. Take out the midlow. The way you shape the eq will define the sound of that kickdrum.

Overheads go left and right.

If you use a kickdrum, snare drum and a left right overhead mic just in front of the kit you will hear a much more clear drumsound without any processing. It is when you choose to fully mic up a drumkit that the crosstalk builds up. So when you do so, you need a noisegate and drumbus compressor. Or allso a compressor on kick and snare.

Hope this makes sense. A drumsound is as digital right now as any synthesizer. So there are alot of recepies out there and loads of different sounds to be had.