which tomtom to buy s/h to run truck

which model of tomtom can i buy s/h cheap to run truck?
i know its best to have 64mb ram.

i was thinging maybe go 710 would do the job.
any advice would be welcome.

thanks

Go for the X20 / X30 range.
A Go720 is a good choice, same for the 730.
If you want to go cheaper take the 520/530.

many thanks for fast reply, will start searching.

No worries, you're welcome!