I am sure if you provided more information on what exactly you are looking for in a boat, where you boat, and how its used, you will get a lot of suggestions to look into. Are you trailering it? Just using it for cruising or water sports? Why just Sea Ray and not other brands? Budget?
The reason for a lot of 5.0 engines is the outdrive. Upgrading to more horsepower would likely lead to an upgrade in drive as well since the 5.7 is at the limit of what an Alpha One is rated for. Sea Ray shoppers are typically not big spenders and work off of a budget as it is considered an entry level boat. Not that there is anything wrong with that, I own a Sea Ray myself, but I don't need a lot of fancy gadgets and trim packages. I have the 5.0 on my 19.5 foot bowrider and I would say that I wouldn't want a much bigger boat with that engine in it.