A couple of questions:
- Does your dojo do weapon-to-weapon contact or only solo kata?
- How long have you been practicing?
If their is contact with other weapons then I would definitely go with one of the higher end options. I have one from Kingfisher (George posted a link) and it is very nice with a near indestructible tsuba. However if you only do solo kata I don't see the need to go to that expense. Which brings me to the second point. Many times I've seen new folks get some really nice gear only to leave after 3-6 months. If you're really new I'd go with the least expensive bokken that will allow you to safely practice in your dojo. If you've been at it a while and think you want to stay with it then get yourself a nicer one.
p.s. Get the tsuba. If you don't need it you can take it off.