What about "full range" monitor like Totem mani II, AMR, Dynaudio C1, Focal mini diablo? Would speakers like that be an option.
Also does you (pre)amp have a pre out. I don't think a sub should be connected to the high level output. To be honest I think a sub can be used in 2 channel audio but only if if you have some way to keep the low frequensies from going to you front speakers. A way to cut of your current speaker from recieving any signal abouve 60hz and let the sub handle the below 60hz frequensies.
I hope I make sense
Also does you (pre)amp have a pre out. I don't think a sub should be connected to the high level output. To be honest I think a sub can be used in 2 channel audio but only if if you have some way to keep the low frequensies from going to you front speakers. A way to cut of your current speaker from recieving any signal abouve 60hz and let the sub handle the below 60hz frequensies.
I hope I make sense