I find it interesting that knx is being so roundly recommended now. When I put my house together it seemed that the stronger recommendation was z-wave. I went knx, because I would always take wired over wireless.....and there is a wider range of devices and cosmetic options.
Anyway. You wont regret knx. There are some options that can make a budget go further by doing more - for example the InZennio Z38
which is a nice touch panel/switch with a built in thermostat that can control heating/cooling, blinds, scenes, and act as a switch. There are some room controllers that have inputs and outputs built in which can be competitively priced (I picked up an ABB RM/S 1.1
for just over £100, new on ebay, which is a bargain). Also there is a thriving second hand market (see ebay, mainly in Germany) - second hand knx inputs and outputs tend to be pretty good, as it tends to be made to a very industrialised build quality. I've picked up a number of things cheap that have not given me any problems. You can get knx at about £15-£20 per output (at circa 16A) if you shop about. I don't think that's too bad. Inputs you can get cheaper.
It depends on whether you can be bothered to shop around, and what your attitude is to second hand/ebay.
The one thing you do need to be aware of with knx is that you need to have the software to commission your system.
It's not cheap.