First of all, that was an excellent post from Chris O; he did an excellent overview of the whole picture of passives.
I just wanted to add a few things. Given the perfect circumstances of proper interconnects, amp sensitivity, and your source's ability to drive the signal to sufficient volume, a passive does offer much in relation to transparency and detail.
What you CAN lose, however, is a bit of the midrange drive and warmth, along with a slight lack of body. Really, it seems to be a tradeoff, depending on mood. I have both passive and active stages. Given the option of a colored, less than transparent, so-so preamp, the passive DOES win out must of the time. It just sounds like the grundge and noise riding along with your signal just vanished.
However, when comparing the passive to an excellent, transparent, dynamic active preamp, the choice becomes far less clear. In fact, I would have to say that after listening to a passive for awhile and inserting a fine active stage, you are almost shocked at the drive and midrange warmth it adds. Indeed, you almost wonder WHY you ever opted to put the passive in! Alas, the same holds true in the reverse...
Personally, I like having both and passives are so inexpensive, that it makes sense to either make or acquire one.
Yet, given the proper resources ($$$), I think an excellent active preamp beats out the passive in full range warmth, drive, body, and even musical detail if really done properly. This seems to especially hold true with a 2A3 SET as the midrange really does nicely with a proper active stage.
I imagine, as I said before, the Laurels might do well with both. One thing you can do, order a passive from one of the online locations that gives you a 30 day return policy (AA). Consider it an extended audition. If you are not happy, simply return it with a bit more education gained in the process.
kh