Yeah, basically, pick a model, any model. 1000 if you want some heft and don't mind the lesser RAM that takes away a rather small handful of emulation advantages. Early 2000 if you really, really want to be comfortable in case you somehow actually manage to hard brick the system, which, at this point, would be a feat of pure skill. Later 2000 or 3000 depending on your screen preference, as these are most likely to still be excellent condition systems if bought secondhand. The GO if the form factor works as it does have the super convenient built in storage. Last and certainly least, the E1000 if you don't mind the gimped version of the system. Not necessarily horrible, but certainly the least of all the available PSP models.
People prefer 6.60 for whatever reason, although I like sticking with 6.20. They're really the same thing at this point in terms of support. If you end up getting a system on 6.61, there are a couple different downgraders available that work perfectly (I speak from experience). Most systems out there can use the permanent patch for the CFW as well, which completely removes the need for the fast recovery whenever the system is fully restarted.
All in all, PSP modding has been made so easy and painless it's almost ridiculous.