Should I bother to try a subwoofer?

As low as it will go .

I disagree with those who suggest a sub is just for explosions and crashes. REL has a great reputation, it should be a good addition for your Dynaudios. The mistake many make is in the set-up. I find that setting the crossover too high at first makes it easier to find the right phase adjustment. Then set the crossover and output levels too low and inch your way up. When properly tuned in, you should be almost unaware of your sub- until you turn it off. Although there can be benefits using the crossover to cut the lows from your main speakers, I usually like running the speakers with fullrange signal, you may experiment with plugging the ports.
If you get a good price, I definitely say go for it. You may love it, the set-up can keep you busy in a fun way, and if it doesn't work out? It's a REL, and should be easy to unload.

Many thanks to all who responded--I've learned a lot and will be actively looking for a sub. Unfortunately, in the meantime the Strata III has sold (he who hesitates is last), so I'll be searching the archive for threads on good mid-fi subs that might match up well with my Dynas.

Blkadr makes several good points. I run my main speakers full range down to around 50Hz then using a good SPL meter and test disc, blend the subs in near that point where they start to creep into the lower midrange then back them off just a bit.

That's what I like about the REL's, you don't have to have your main speakers going through a filter mucking things up.

Tmsorosk, you make the dumb blanket statement, bad grammar and all, and I'm the uneducated one? As pointed out by Macdadtexas, few people own speakers that go much below 40Hz. They're giving up a lot of what's in those grooves/digits. If you've "tried at least a dozen subs in the last 38 years" and been unsuccessful, duh, perhaps you bought "the wrong speakers", I mean subs!

As a former full range speaker user and subwoofer hater (except for pro sound use) I found Elizabeth's comments understandable but less valid than usual when applied to a topic including REL subs..."Rock" music can certainly have a lot of bass (as does a lot of the jazz I like...Brian Bromberg anybody?) but the beauty of most RELs is the amount of gain, phase, and frequency adjustment inherent in their design. I adjust the output level frequently (in small steps...I put a "chicken head" amp knob on there so my greasy little fingers can "feel" what I'm adjusting) to fine tune the bass response for certain bass shy or bass bloated wall shaking recordings (do I agree with ALL of the engineering decisions made by the faceless strangers who messed with the sound of my recorded music? NO!)...otherwise impossible with my (and most everybody else's "high endish") preamp. It's nice to be able to do this while leaving the rest of the signal chain and main amp signal unmolested, as, for my tastes, this is all the adjusting my rig needs...plus it allows me to continue my sonic dominance over these things as, after all, I am the "decider".