Best dual SIM PDA?

Dear All.

I am looking for a low cost phone/handheld/pda for myself. I find it difficult to found out of specification, which to choose, so I give the options I am looking for.

1) Dual sim, preferably both connected at the same time. When I am outside the contry, I have a different sim card with me. Best sollution for me is that i dont need to switch the sims. If only one sim works at one time, is also a sollution. Would be nice if there is a auto detect function based on the network names (one network within the country is used by both sims, so in principle, if this network is found, SIM1 should be active, if not found, SIM 2 should be active.

2) Would be nice that it has some functions should as navigation/GPS build in. E-mail fuction + calander/agenda would be nice to. I would like to run TomTom navigator software.

Which models are best for the above wishes. GPS chip must be good, as some low tec versions don't work inside cars that well, which would make the feature useless.

With above needs covered, a good brand would be nice (nokia, etc.), however cheap is more important (although with low price difference, brand comes first).

It is also possible for me to buy in China, if someone knows a good type made there (although in general, Chinees made PDAs have low quality). As I am there for work in February, it might be a option though (as a few hunderd dollar differance in price does allow for taking a low quality risk).

Awaiting your valued input on this subject.