I dunno what I prefer. I like both narrow and wide string spacing for different reasons. I like wider string spacing for slapping, but I find myself more agile (i.e. soloing) with narrow string spacing. I owned an MTD 535 for a short time and that had 19mm string spacing and was 35" scale. The low-b was very tight, but that was the only advantage I could make out. The neck is incredibly comfortable which made it easier for the extra finger stretching I had to do due to the wide string spacing. I think that is quite important when buying a bass with a wide string spacing...comfort. I have played many basses with wide string spacing that were quite simply painful to play (and that is coming from a guy with very long fingers!). My Warwick 5-strings are both 16.5mm I think, which is pretty narrow. I don't like the feel of the 20mm wide string spaced models (Broadnecks as Warwick markets them as). Warwick can't make me an 'inbetween' spacing because of machining restrictions. My ideal spacing would be 17.5-18mm. I'm still waiting to find a company that can do that for me.
DW, if you like the Warwick Streamer but you can't swing with the Stage I model being that it is a Broadneck model then I would recomend the Stage II model which has a narrow spacing. I have a custom built 5-string that is awesome. The standard model is quite a tone monster in its own right and for a high end bass it definately does the business, as you would expect.
One of the most user friendly 5-string basses that I have ever played on is the Music Man Stingray. They play great, sound great, look great and retain their value pretty well. I think is the perfect starting point if you want to upgrade to high-end basses. I would try to find a 2nd hand model in good condition that was built between 1990-1994 with a birds-eye maple neck. The quality of the basses dropped off after this period...they stopped using the birds-eye maple and the wood selection and build quality has never been the same after 1994ish. You often find one in good condition on Ebay going for about £750-£1000 (thats about $1650-$1900). Brand new, they are still pretty good and hard to beat with all the other basses out on the market for the same price, but I would no longer say that they are a high end bass anymore...not like they were considered 15yrs ago.
Another thing to consider when buying a high-end bass is the re-sale value. Afterall, you can spend a heck of a lot of money on a great bass, but also lose a lot if you want to sell it on. You have to treat your instrument as you would with a car. How quickly will it de-apreciate? What is the general appeal for the instrument? Is it made by a well known company? Will it be used in a sweaty night club 5 nights a week or will it be a home or studio instrument? All these things have to be considered. For example...my Warwick Custom Dolphin has a trade retail price of £2550 and I know that I willl only get a best re-sale price of around £1750...even in mint condition. From the day that you buy a brand new high-end instrument (especially custom made) you can knock off at least 25% of the trade retail price that you bought it for on the very first day that it is in your hands. On a similar note, the same principles apply to buying vintage instruments. I could have kicked myself really hard a few years ago when I sold my Fender 73' Fretless P-Bass. First off, I had no idea that they were quite rare (Fender didn't make many fretless P-Basses back then) and I also made the mistake of installing an EMG electronics package and selling the pickups to a local tech. I could have sold that bass for over £2000 to a collector (a heck of a lot more than I bought it for) and only because I sold the orignal pickups I lost £1000 on the collectors price! You have to treat your instrument as investment to possibly buying or trading for another bass and it can be a fruitful experience or a very painful one. It might be an object of desire for you and might serve you very well, but you also need to have a business head on your shoulders too. At the end of the day, you will always have to spend money when buying a new bass...even if you part-exchange, but limiting your losses takes a lot of careful thought and research.
I know I added a lot more that I needed to for this post, but I thought that this could help anyone on LGM considering upgrading into the high-end market.