Scott, I would consider the Titleist Hybrids.  As far as the lofts, I would have you go to a Titleist Fitting center or demo day to try out the various lofts and see which works best for you.  I think though you are on the right path with 17 and 21 as a starting point though... Good Luck!

Scott,

Chris gives great advice.

Here are some things to think about.

Are the R11 Hybrids 16* and 19*? Do you have them at stated loft? Do you have any flighting issues with those?

What is your typical ball flight? Do you need help getting it up or do you want to keep it down a bit easier?

What did you decide to go with hybrids when you purchased your current clubs?

What do you irons look like? 4 iron is your lowest?

What is your 3 wood loft?

Think about your gaps where you aren't covered.

Hopefully this helps get you started. 

I took the 3 wood out of the bag a few months ago, and purchased the 17* 913h.  I don't see myself going back anytime soon either.  I love the 913 hybrids.  I've got the 17, and the 21, then the 4-P.  It might be a few yards shorter than my 3 wood, but for me, I can hit it a lot straighter, and when it's a bad swing, it only fades 10-15 yards, and not 30-40. 

Agree with the guys on Titleist Hybrids......I switched from Adms and have never looked back........I carry a 913H 17*, a 910H 20.5* and a 913H 24* the 5(26*)-PW(45*) irons......910D3 is a 10.25* and 913F is a 14.25........50.08 and 56.10 Vokey....I play the senior tees and use my 17* hybrid a lot off the tee and it is an awesome club.........think I just about have my lofts down for my age 67...I too like the middle as often as possible.......