How to upgrade my Rega Planet based system

I would like to second the recommendation for a sub in your system. I once had the Rega Planet and Mira with Jura speakers. For a time, there an REL Storm II in the system, and it helped bass extension greatly. It was easy to integrate and was very "musical." By the way, The Rega Vulcan is made by REL. You could prpobably find a good used REL Strata or Storm for about the same price as a new Vulcan. Used Vulcans don't turn up very often. Either REL unit will be more powerful and will go deeper than the 8" Vulcan. In my exporience, the Rega gear will benefit from power cord upgrades. The stock ones are as cheap as any I've seen. I wouldn't go overboard on the power cords though.

I third the recommendation for a sub. A REL, Rega (which is designed and made by REL for Rega), or ACI sub would be the first choices.

If you like the upper octaves of your system why risk changing them ? Also these subs will take you down to 20Hz and give real bass-drum kick. I would bet you'd be looking at a lot of money to upgrade your amp and speakers to achieve the same.

All of the above; a subwoofer, power cables, and conditioning.

Buy REALLY expensive power cords. Like Siltech Compass Lake. Your dealer will be glad you did.

Subwoofer is the way to go. You'll be set free...I love my Sunfire Artchitectural Subwoofer. 10" single front firing, made for 2 channel listening. It's a shame you don't hear about this baby enough on the 'gon. It's fast, extended, tight, and integrates beautifully with my M 20s. It lists for $1400, but can be found nicely discounted (new) for less than $1400. It's an 11" (45 lb.) cube with a 1200 watt amp. (Sunfire also has the Architectural Signature, which is a 12") If space is a factor, this may do it for you. I compared it to the Velodynes and the comparable Rel.