When building a HT system the most critical speakers are the front 3 - often referred to as LCR (Left, Center, Right) - and you really want those to match (in a traditional 5.1 system about 75% of a soundtrack comes from the front 3 speakers). Using a center, arguably the most import speaker in the entire system, which isn't 'voice matched' to the L/R speakers is not advisable as it tends to create an imbalance in the sound field.
It's ok for surrounds to be in-wall or in-ceiling, because of how little they do, but the front 3 shouldn't be. One of the things a speaker designer will try to do is minimize the width of the panel the drivers are mounted to. That's an attempt to reduce the affects of defraction, where sound bounces of the flat surface and ultimately creates distortion. When your speakers are mounted in a wall you have the exact opposite, a huge front panel. That is never a good thing. You also want to keep the front 3 a somewhat even distance from the listener(s). While modern auto-EQ systems like Audysee can compensate for a degree of distance adjustment, if you have them too far apart it can cause the sensing algorithms to miscalculate.
Depending upon what you're looking to achieve, the Jamo J10 may or may not be sufficient. If all you want is some mid-bass sound it will likely suffice, but if your intention is to recreate anything of substance in the lower frequencies it will fall well short of that. Typically people will be more sensitive to deficiencies in their bass than anything else, so you may want to reconsider your sub choice. What type of budget are you working with? Are there any limitations to consider (size, cabinet finish, etc)?