I would recommend reading some on-line reviews and making up your own mind considering your budget. Don't get caught up in needing to buy a "stereo DI box", I think it limits you unnecessarily. Two single-input DI's would achieve the same thing.
I use a cheap Behringer rack-mount DI unit for rehearsal (the DI4000 mentioned by Harry above) which does the job more than adequately considering what I paid for it. However for gigging I go with the Key Largo I mentioned earlier, alternatively depending on the gig/band I have the sound engineer provide his own, which I'll specify in the tech advance.
The stereo DI box, unless specifically made to run in stereo, is simply a couple of DI connections put into a single chassis for simplicity. In fact, I bought the Pyle Pro DI boxes because I always run stereo. Mono is a 4-letter word for me and with all of the sonic landscapes and depth we create with our rigs, running mono is not good.
I know that there have been many conversations about playing live using stereo/mono, and that may be beyond the scope of this thread, but I have played through both Mono and Stereo PA systems and prefer stereo
I think that we all prefer that.
Back when I was getting started, MANY years ago, I used two single DI boxes for my live rig. I got stereo that way. With my rig now, I fashioned a setup in the back of my 6-space rack to house one of those Pyle Pro Stereo DI boxes. It is mounted in the back of the rack and if I ever need to use it, I reroute the master outs from my submixer to go to that and then run the XLR cables from the DI box to go to snake.
Since I have a wireless headset mic AND an IEM, I now, with the band I am currently in, actually stack my 6-space rack on top of our rack snake and plug direct into it with 1/4" TRS cables. I cannot even remember the last time I used the DI box - but it is there if I need it.
There are many options for DI boxes, but the thing to remember is that if the user wants to run stereo to the FOH, the user will need two DI connections, whether they are in separate boxes OR in a single chassis.
These are the Pyle DI boxes I currently have:
Professional High-Performance Dual Passive DI-Box - 1/4'' Instrument To Balanced & Unbalanced (1/4''/XLR) Direct Box
www.pyleaudio.com
I have a couple of these as well, but have not used them in a very long time:
DOD 260 Passive Direct Box. Condition is "Used". Shipping continental US only. Not much to go wrong with this.
www.ebay.com
It is important to note with these DOD DI boxes, they have dual inputs, but only have a single output. Plugging a stereo connection into this DOD DI box will yield a mono connection, NOT a stereo one. When I used a smaller keyboard rig of just two keyboards, I plugged the left outputs of those two keyboards into one of these and the right output from those two keyboards into the other DOD box - that is how I maintained a stereo signal using these boxes.
Here is another DI box, this time from Rapco:
www.rapcohorizon.com
These links are for reference only and certainly not for buying from the company direct or direct from eBay.
Grace,
Harry