I think 150's would be underpowered, the 258 alan has has less beam, beamier boats usually require more hp to get on plane. Heard a lot of positive replies on this site from twin 175's, and 200's seem to be most common. 175's would be enough, but depending on which engines your talking about, sometimes the jump to 200 will give you just as good or even better fuel economy if it is based off the same block, also gives you more hp to stay on plane when seas are tough. Twin 150's would be ok in flat calm, but in anything less would be a pain to keep on plane at a comfortable speed or even chug with your rig. Look into what engines your looking for, since they are EFI's, are you talking Optimax's, HPDI, or another brand/model? They all vary a little, decide what brand you would perfer, and have a back up so you do not limit yourself to much, and then do a comparison with those engines in various sizes, it will give you a better idea and a better basis. Decide what dealer you would perfer to do your maintanence, that may decide what brand to use, having a trusted mechanic who is local and dependable is just as important as having a good engine, if not more so.
Personally if your looking for EFI's, twin Yamaha 200 HPDI's would be my choice, I own one, it was the second boat repowered in NJ with one(done in 2000) and we have had 0 problems and it has been great. Economy is comparable to a four stroke, and sometimes better, and your cruise will be higher. It will give you plenty of range, good speeds and be economical as well as reliable. A 200 Opti will burn slightly more fuel but they are not too far off. Watch what year Opti you look at, earlier models(roughly first 2 years) were problem prone, newer one's were excellent motors. I know plenty of guys with Opti's and fish a ton of boats with them, but to me they are noisier and I've been on too many opti powered boats that have broken down, out of just as many guys with HPDI's, only one had an issue with his block, under warranty and replaced by Yamaha.
Once you've narrowed it down to a brand it will be easier to determine if 175 vs 200 vs 225 would be better, although i think staying under 200 would give you the best economy with plenty of power in most cases.