Bi-amping versus Bridging for NAD S200's

I currently have 2 NAD S200's running as bridged monoblocks driving a pair of Paradigm Studio 100's. This was easy to set up useing the same interconnects and speaker cables as I originaly used with a single S200. The bridged monoblocks gave a noticable improvement over the single amp. Strangly enough this improvement was even noticibale at low listening levels.
I have tried vertical bi-amping useing cheap interconnects but as you might expect with cheap interconnects the sound was not as good.
I am about to upgrade my intertconnects and speaker cables and would like advice on which of the 3 setup options (vertical biamping/horizontal biamping/bridged monoblocks) would give the best sound. I am not chasing extra high listening levels. A single S200 gave more than adequate volume.
Whilst it would be great to be able to try all 3 options, with decent cables it would be expensive. Particularly when biamping requires twice as many interconects and the relative lengths for speaker and interconnects for vertical and horizontal biamping are different.
To further complicate the issue the NAD S100 preamp I am using has 2 sets of unbalanced RCA outlets but only one set of balanced XLR outlets. I am currently useing the balanced outs for the bridged monoblock setup.