there are reasons that Maemo 5 is no longer around in the retail and one of those being it would have been a killer OS once set free from the Nokia imposed 2009 hardware restrictions and ported to a range of different form factor devices with enough RAM and decent processor speed.
People in the industry have paid considerably to make sure to never see this happen.
So it is normal that you have to pay premium to get a preview of what could have been.
I don't think that a 2 year old processor is a restriction for Maemo 5 or even Sailfish.
The thick form factor of the N900 (so comfortable to hold) is missed over here but that is totally subjective matter.