Nice idea. An entry level machine that performs well is needed. Bear in mind that the other thing that is needed is a much better applications bundle.
We bought a mac mini because the bundled apps expanded what we could do with a computer (compared to what we could do on our RiscPC's and Iyonix) and made some things we do a lot easier.
It is of course a chicken and egg scenario, the more the market expands the greater the chance that more software will be written. Thus computers such as the (proposed) A9home could help by expanding the market.
Interesting times. Maybe it will even be worth considering purchasing another RISC OS machine in a couple of years time when a machine that makes the Iyonix look slow appears, and RISC OS applications have been ported/written to plug the remaining gaps (as the Firefox project should do for browsers).