Your budget, time-plan and experience will determine what you should do. If you have little/no experience then I would suggest picking up a 30ish foot mono to learn the ropes on. After you get accustomed to sailing or if you already have experience then go for the cat. For a couple, 50' would probably be the maximum with the sweet spot being 38'-44'. Older boats will require more refitting to bring up to safe cruising standards. Generally cat design has not changed much from 2003 but anything much older and you will be sacrificing structural integrity, headroom, amenities, weight capacity etc not that these are just with old boats, many new boats are just plain not suited for cruising.
Your exact budget will determine what brands you would be looking at.
You can learn more about peoples experiences with cruising cats by reading their blogs, since you show an interest in the anteres, check out this link: SALARN
or more blogs at this site:Catamaran Blogs - projectfiji.com