I don't have a specific in wall speaker to recommend, but if you want to play music in full surround, like a multi channel SACD, then I would try to get all of the same exact speakers, or at least as close to the same as possible. Stick with one manufacturer and within the same line of speakers. This is less important for movie watching as the surrounds play mostly effects etc., so for a theater room the surrounds can be from another brand if need be.
Also, most people set the crossover between the speakers and the sub at 80 Hz or so. That means frequencies below 80 will be played by the sub, but above 80 by the speakers. But, that is a gradual handoff, so it is a good idea if the main speakers can play below 80 Hz so there is a seamless transition to the sub. Look for spec that lists the -3 dB point at around 60 Hz or so.