Audio Research Classic 30: how does it compare to ARC current power amps?

If you're looking for a great deal and your speakers are fairly efficient  the Ref 75 SE is a remarkable amp and for my money would be the keeper of the bunch that you've named.  The VT80SE is also a great amp however and those do come up on the used market.  I think you would find the sound rather similar.  The VT80SE has the new self-biasing circuit if that means anything to you.

@ shastasheen
We used to sell ARC stuff from the late 80's to 2008. They were not for everyone looking for the "tube" sound. ARC stuff always had harmonics that induced a "clarity" to their reproduction as opposed to "beautiful".
That being said, the new stuff brings forth all of the old "house sound" in an even more delineated way. Bass is crispier. Midrange more frontal and highs more shimmering. While there might have been some growing pains while Mr. Johnson was looking to improve the ARC sound until his passing, dryness is gone in my opinion while maintaining  the "heft and weight" reproduction should have.
If you are looking for "realism", the new equipment brings that home in spades. 
In attending an audio show in Las Vegas, Nevada in 2012, the most realistic sound I have ever heard was with the Reference 150 separates, their cd player at the time, through Verity speakers.
Some there turned away while I stood in amazement that this reproduction could come so close to realism.
It remains a matter of taste.

This may not be of much help, but since no one has chimed in I'll give my thoughts. I used to own a pair of Classic 150s (converted by ARC from M300s).  I assume that the Classic 30, like the 150s, runs in triode and also has a solid state input stage.  I ultimately felt the Classic 150s were too "dry" sonically for me--i.e., the sound was not as rich in the midrange as an all-tube unit, tilted more to the high frequencies.  Having heard the more recent ARC designs, that dryness seems to me to be gone now, so to my taste I'd go for a newer unit.  If I had an old D250 or another of the early ARC units like daveyf I might not want to give up that sound, it is an addictive and classic tube sound.  In your case, you seem to like the CL30 sound, so I'm not sure how you'd like the newer units, which will have more power and bass control but will be more harmonically fleshed out, which might lead you to feel they don't have quite enough detail. I do think, though, that there should be more than enough detail in the newer units to satisfy you, as the ARC house sound is still about high definition.  What speakers are you driving?.  

@shastasheen65  You post a very interesting question. How far have ARC come in their amp designs from the Classic 30 to today. I used to own and love a ARC D70Mk2...a superb amp. I did have the opportunity to compare it with an ARC Ref 75 and IMO the D70Mk2 was NOT embarrassed in any way! In fact, in some ways the 'gestalt' of the older amp was more harmonious to some forms of music, particularly jazz, IME.
Whether this holds for your question, i do not know, BUT i would be interested also to see if anyone has this experience.