The CV5 and RX are two completely different portable amps, the former being an hybrid unit using tubes in its signal preamp section, while the latter is a fully solid state one.
I own both and though I was initially of the idea that I could forego the RX while waiting for delivery of the CV5, I had to change my mind soon after a few listening sessions with the two amps.
The amazing news is that if you love the CV5, you will equally enjoy the RX - since the sound signature is the one ALO is well famous for.
But what is even more important is that the RX is in its own league when paired with iems. Although the CV5 comes with a flexible gain selector, in my opinion it's still an ideal amplifier for headphones or less sensible iems - otherwise even at the lower setting the hiss will be around the corner. On the other hand, the RX is a perfect match for highly sensible iems and it will deliver the same or very close pleasant experience that the CV5 can offer with less problematic/peaky headgear.
The bottom line is that I would never part with my beloved RX, which is still my portable amp of choice for particularly sensible iems.
I would easily recommend that you go on and also add the RX to your arsenal... it will surely come handy and pay you back with a great hiss free sound, whenever needed! You wouldn't regret it!
Cheers,
Marco