I have the Vegas.
They're my first 'TOTL or thereabouts' IEMs. Not to say they are indicative of all TOTL options, but you don't *need* this level. Not if you can't be comfortable spending the money. I'm not 100% sure I am but screw it, I'm still young and single enough to not be fiscally responsible. It does make me realise how good the FLC8s are. You are absolutely right to demo since you have the opportunity (I do not).
Not to say the Vegas aren't doing things the FLC8s can't do, because they are, and not just in the sense that (out of the box at least) they try to collapse your skull with bass. The mid-range is weird and remarkable in the sense that it's not forward, it can't be against that bass, but the clarity is still breathtaking. Particularly with vocal detail, backing vocals really come to life. But its not the same presentation as the FLC8 on the whole, objectively its an upgrade but not directly. I suspect aspects of the Vega will be divisive, by design. Definitely worth trying of course.