Well, right now the compressor plugin situation is not the best.
I am not a big fan of the TAP Dynamics processor.
My port of one of my favourite compressors (see the forum thread New plugin: Molot Lite Mono) is done and I play with it, but right now it is not downloadable from the plugin section of the MOD.
Another great compressor would be the compressor of the Invada series. This plugin is not in the stable plugins right now (I don’t know really why - it works great).
If you want clean compression your best (and maybe only bet) right now is to use the TAP dynamics with a compressor or limiter setting. Here using the offset gain control is the key - so you can move around the fixed value for the compression (4:1 compression at -6db).
My favourite stable plugin right now is the TAP Sigmoid Booster. Don’t let the name misguide you - it works really well for compressing bass. It is not the cleanest compression you can get, but it works fine for me.
Slowgear didn’t work for me, but I don’t know the original pedal and so I don’t know if it’s just me.