[disclaimer: I just woke up and am an avid non-computer noise maker who's moved to modular pretty much but still uses the BSP as the master sequencer]
I own a Beats and a Circuit and find I don't use the Circuit to sequence anything but itself. I'm lazily trying to sell the Circuit as I'm fairly nonplussed by it's internal sounds. The sampled drums are not bad, but I really don't like having to run a piece of software to edit/change them. I'd rather use a non-propriety audio edit to edit samples if I am to use a computer for that and then load samples via an SD card of some description, as I can with my Microgranny 2.
As far as programming the Circuit goes, it's melody sequencers are great fun and have a wonderful way to play the sequences as one-bar clips or a long 8 bar sequence. I'm looking at getting a Novation SLmkIII to replace my Circuit so I can get the sequencer with the sounds. Not that the sounds are not any good, they are straight out of the Nova and are wonderful, just I am not a preset sort of person and like to program a little deeper without using a computer to do so.
With regards to the Volca sample, if I was you, I'd really research that machine before you drop the cash on it. It's very idiosyncratic and a lot of users find that once they move off of it's sequencer they start having troubles. I don't own one but I'd not buy one either due to the way it runs when externally sequenced (and the manner in which samples are loaded to it).
The BSP is my main sequencer. I love running drums on for a start. Setting up a drum map does require a computer, but once you to that it's all on the machine. Running the Volca Beats with it makes the Beats way more versatile than running the Beats on it's internal sequencer. Beats' sequencer is fun and novel, though can be limiting as it's only an 8 step sequencer. The BSP opens that up and by setting up a controller map on the BSP to control the Beats' MIDI parameter give you a bit more usability than the tiny little Volca miniknobs.