HTC TOUCH3G OR HTC VIVA OR HTC TOUCH GSM

Dear all,

I want to buy an phone with PDA capabilities-so zeroed in on three HTC Phones.
Suggest me which one to pickup.

and

I would like to know

1)Are any better alternatives to these phones(With a good pdf reader and multimedia capabilities) within the given budget.
2)Are HTC phones worth the money in terms of battery?
3)If not HTC -which is next best alternative to view excel,pdf and power point?

Budget limit-20k.

Regards,