As far as comparing the monitors, I'd say it's quite a difference between 3-way Reference and 5-way Reference. But then again, it's my opinion and I haven't heard anything better than 5-way. 3-way's are, in my opinion, very good too and these were my primary and only monitors for more than two years until I came up with the 5-way's. They share some similarities of audio reproduction, i.e. their presentation is neautral and natural. The 3-way's, however, build their sound signature from the bass up, which makes them warmer in comparison with the 5-way. Everything is in place, liquid and natural but as if to look at the same thing from a different angle and perspective slightly. 5-way's are a lot more more refined in the whole spectrum and it's clearly audible, but 3-way's are nevertheless good as well, I think. 5-way's, in comparison, have even deeper bass response (though the deepest notes are activated when they are in the recording), the mids are extended in a huge amount and the highs as well. The 5-ways can naturally go up to the limits of one's hearing as they can produce a sound without a roll-off at least beyond perceived 23,5kHz. In comparison to 3-way's they are more flat and balanced to the human eardrum (in fact this is the most reference sound I have ever heard). It's also true about 3-way's, but they have a slightly different focus on their sound signature and reproduction. In one word, I'd describe 5-way's as super extended and refined in every aspect 3-way's.
However, taking into account that you enjoy your Westone 3's which have quite a dark sound signature and the music you listen to, you might be quite happy with 3-way's. I have very similar tastes in music and ever since having created 3-way's I was very happy with them.
Personally I gain a lot more from 5-way's (it's in a different league to my ears with a whole lot larger resolution, frequency response and unimaginable levels of details, transients and PRAT among other aspects), but it depends no your tastes overall. If you are happy with this kind of signature as presented by a universal version, I think you can already be happy with a proper 3-way Reference custom.