you can find what you are looking for on almost any cruise line by looking for their "older" ships (that being a relative term these days) and probably at a great rate if you or your travel agent, do your homework !!
I agree with you about the mega ships, I try to avoid them as much as possible because the older I get, the less I like crowds (and that's funny considering when I was 18 I was at Woodstock !!!)..however, I am very close to succumbing and going on the Freedom of the Seas next May when it is being chartered to the Tom Joyner Foundation..
I've been cruising since 1976 and my still all time favorite was on Carnival's Mardi Gras which if it were still cruising today would be considered "antique"