I got the 6310i for exactly the same set of requirements - I can't stand those small phones - just too fiddly and weak.
I only use it as a phone or as a modem sometimes, but the mic gain and sensitivity are good, the speaker is loud enough to cope with very noisy environments, the battery lasts a week between charges, and I use it a lot, and it is solid as a rock. The voicedial function is pretty good, too. It works well in the car.