Which one of these Roland models are newer XV, or JV series?
Are synth modules(Roland) are "parallel" with the keyboards, for example: Roland Xp-60 with XV-5050. if yes what are they?
Are there other besides XV and JV series?

is there a web site to hear demos of JV, XV modules?

XV is the more recent of the two. JV were the older models. JV take the SR-JV sound cards while the XV take the SRX sound cards. Even more confusing, some of the SRX sound cards really just contain SR-JV sound cards! And then there's the XV-5080 which can take both!

Bottom line is the XV is the more recent of the two models. You can go to www.rolandus.com and listen to demos. Click on the Fantom X keyboard and then go to the SRX Sound Board interactive demo. It's actually pretty cool and you can hear all of the expansion modules when you drag them onto the Fantom.

Tommy