Wow, this has been great advice! I really appreciate the hands-on perspectives. I've been continually impressed with PentaxForums since joining in how measured and helpful the advice is. I rarely see the typical "this lens sux dude" comments like on so many other forums.
I think I've been convinced to go with the DA* 300mm. I'll just bide my time until someone develops an SDM-compatible converter for it. I have to admit the Canon 300mm f/4L lens was my favorite lens and was the hardest to part with when I jumped ship. I even had the 70-200mm f/4L IS and just didn't connect with it like I did the 300mm. I have a feeling I'm just about to acquire a new best friend.
Thanks for the feedback on this issue, borno, Mike, C-R, and Steve. Thanks for the pics, borno! They're great close-ups with the lens. I'll keep an eye out for that T-C in the marketplace (hopefully posted late at night so I'm the only one ready with a PM). This advice has really has helped me find a solution that will work for me. So, anyone have a gently loved DA* 300mm lying around that they aren't using?
JK. I'll be posting in the Wanted area but will realistically just plop down the cash for a new one since it's cheaper than the budgeted amount for the 100-300mm anyway.