stereo amp vs monoblocks, any advantages?

You gain absolute separation between the channels of the amp and much greater flexibility in amp placement. You don't have to worry about such things as weather to biamp horizontally or vertically. You don't necessarily gain extra power, theoretically you can make a stereo amp of any size, but two monos are easier to manage than a stereo one, and , as previously mentioned, what is going on on one channel never affects the other. Monos take more room, 2 power cords and are inevitably more expensive, otherwise they will always be better assuming same quality otherwise.

When you are buying a "Dual Mono" amp on a single chassis check on what they mean, the term is used very loosely, not consistent even with the same company. Some of the Musical Fidelity amps , for example, have two separate transformers, one for each channel, and others have one large for both. Both are called 'Dual Mono". The more parts of the amp that are shared between the channels the more they will interact with each other.