Thomas:
From the standpoint of justifying your investment...that's a lot easier to do with a used Alembic (this coming from someone who has purchased two new ones and two that were pre-owned) than a new one. Used alembics hold their value quite well in my opinion. New one's, like cars, do not. Whether new or used, however, Alembics play and sound like no other basses I have ever owned and are a joy to use.
As far the difference between a Spoiler and the basses you have been discussing, it going to come down to your personal preferences and tastes as well as the degree to which the bass in question has been customized. Unless you are talking about a Series bass, when it comes to tone, you could probably get your Spoiler to sound pretty close to an SC or BB if you ran it through a Superfilter. These things IMHO provide the ultimate in tone shaping. As for playability, its really personal preference that comes in to play. For example, in addition to the SC and custom Signature I have in my stable, I also own a very nice, medium scale walnut Distillate. I don't find myself playing it all that often nowadays because I really prefer the shape of the necks on the Signature and SC to the Distillate. They are all very easy to play and incredibly high quality basses. The latter, however, just doesn't seem as comfortable in my hands.
Good luck with your search. If you are prepared to be patient, I'm sure you'll eventually find that for which you are looking.