Amp choices

The Aragon and Parasound are both nice amps, but they are different sounding from each other. I agree with others your SF are very nice speakers and I would look at a more refined amp than the Parasound if you're looking to replace what you have. Definitely a more sideway move than a Pass or some of the others mentioned. The Parasound is probably missing the authority of your Aragon, but the Parasound has a better balance. Both the strengths of these two amp will be there with the Pass but at another level. I remember the Aragon well and like the Paragon they both are really good, but they don't disappear; especially the Aragon. The Pass will disappear which is what a great amp should do. I really don't feel I'm hearing my amp but more of how nice my preamp is. 

Merrill Audio Veritas mono blocks will rock the 3's. These amps are refined,musical and will let the SF3's come alive in a way that is very involving and natural. The SF's need power to sound their best and the Merrill's will deliver in spades.

It sounds like a Pass 250.8 is something to look at as a real serious upgrade.  You are correct that the A21 is probably better balanced, but the 8008 has more control of the speakers.  I'm using AZ Hologram ii speaker cables and Wow ii interconnects.  I could probably do better on the interconnects maybe with Matrix ii or something from AQ.     

I would recommend a pbn audio amplifier 

I know this discussion is mostly two channel purists! Presently driving pair of psb imagine t3s with krell foundation 4K and halo A51 parasound amp! Wired wth Cardas clear reflection cables! Parasound amp seems to stage and image psb t3s well! Feeding krell processor with ps audio DSD and PWT pairing ! Sound on given recordings life like! A21 amp I'm sure may be similar! Just my opinion !