If money was no option? I dunno. I'm sure I could find a $5,000 PDA like device. If you stick with a traditional PDA, somewhere between $300-$700, you'd go with either Asus, HP Ipaq, or a Dell Axim. I have an Axim x30 and I love it. I went with it over an iPaq because it is much less expensive, and Axim's are regarded as a bit better. My dad has an iPaq and my Dell is better than it hands down. You definitely want something that is Windows Mobile based though.
If I was going to get a new one, I'd go with an Axim x50. Best screen, fastest processor, ton of features.
Someone might be able to give you a better rundown of Palm options if that is something you are interested in. Check out
www.aximsite.com if you go the Dell route. Great site.