RC-20 :: clear tone loop + sustain 2nd layer

[RemyC <remyc@optonline.net>]

Hi,

I'm new here... god send this website is! I'm getting back into playing...
my guitar's been in the closet for ten years... but I've been asked to dust
it off to play again.

I used to have an Electro-Harmonix 16 second delay but I sold it ages 
ago...
I've been looking for something to replace it, and the Boss RC-20 looks 
like
the safest bet for the money today, unless somebody has something better to
suggest. I have not bought it yet.

I'm scratching my head how I will be able write a clear tone rythm phrase,
loop it, then lead over it with sustain/gain.

Am I going to need two amps and an a/b foot switch to do this, or is there 
a
way with the RC-20 to do this with just one amp? I have an old 5210 
Marshall
and I just bought a MG10CD practice amp. I'm thinking of hooking them up in
sequence. I'm not concerned about loudness. For now I just want to set it 
up
so I can practice writing rythm lines and then layering melody over them.

If I could do this with just one practice amp, without having to lug out 
the
5210, that would be great.

Anybody out there want to start me asking the right questions and guide me
in the right direction?

RemyC