Horizontal bi-amping for 3a Signatures

I have a pair of PS Audio HCA-2 amps that I am currently using in horizontal bi-amping for my current speakers resulting in an improved sound. I also have a pair of Vandy 2wqs. I have almost certainly decided to purchase a pair of Vandersteen 3a Signatures. I am almost certain I read in one of the Audio Perfectionist Journals by Richard Hardesty (which I dont have access to the copy that made the reference to which I will refer)that audio nirvan is attained by employing horizonatal bi-amping for the 3a Sigs.

I just read the 3a Signature manual and it recommends Horizontal bi-amping. As i read further in the manual, even though it doesnt say not to do horizontal bi-amping specifically, it only gives wiring diagrams for bi wiring and vertical bi-amping. Vandersteen goes further to say, the improvement for bi amping is minimal and suggest the "BEST" thing to do would be to buy the best single amp your budget can afford and bi-wire.

My problem is that PS audio does not recommend to use the HCA 2 in the mono block configuration.

Can anyone clear this up please?
Signed confused owner of apair of HCA-2s.