| I own, and regularly use, both the Brick and DB-900. Either makes an excellent DI.
I find the Brick to be very neutral sounding. It imparts just the slightest amount of warmth, but it essentially spits out what you put into it! The great thing about the Brick is that it stays ultra-quiet, even as you max out the volume! Plus, for the price, it's hard to beat as a true professional-quality tube preamp.
I honestly prefer the tone of the Aguilar, though. It adds not only tube "warmth", but a 3-dimensional depth to your tone. It doesn't outright change your sound- but I've always thought it makes bass sound better! I recently did a record with a 5-time Grammy winning engineer. He LOVED the DB-900! One possibly big caveat, however: the DB-900 puts out mic level. I've played some "sketchy" pa's in a few clubs across the country where the engineer wanted more output. Shouldn't be an issue- but it has happened a few times. Also, mic level is not hot enough to properly drive an a/d convertor in a project studio interface. It's something I come face-to-face with a lot more these days. So, for recording, the DB-900 has to interface with a preamp downstream.
Speaking of which, I sometimes actually run my Aguilar DB-900 into the mic input on the GT Brick! If the studio I'm at doesn't have a good pre, the Aguilar+Brick combo is incredible sounding!
I have also used the SVT-DI on many sessions and a few shows. It sounds really good- but- I'll never use one again after the house SVT-DI failed in the middle of a song whilst playing the televised Grand Ole Opry. It was a performance-wrecking moment that I just cannot forgive... Not on national t.v.!
(I voted for the Aguilar purely on tone. It's an amazing sounding unit! Plus, the unity-gain 1/4" out is also affected by the tube circuitry, so you get the benefit at your amp as well!) | 
