I do want midi.
Since I may have bought a 2496 but now realized that having the ability to record multiple things at once to separate channels will be useful...
Is there any benefit to having 2 soundcards? 
No stick with 1 sound card for simplicity.
Yeah I was afraid you may way separate tracks per device... simultaneously.
The 2496 will still give you great results is you want to trigger all synths via MIDI (each on a separate MIDI channel) and mix them with the mixer and record the stereo out of the mixer. Or alternatively, you can create a stereo track for each synth by playing the sequence over and re-record. It's very easy to line up the audio tracks later; obviously the better idea for many synths is a multichannel audio interface... so with 1 pass you can have all tracks separated for EQ and effects.
This is one one those topics that if you clearly defined what you wanted to accomplish... I was under the assumption you wanted to transfer vinyl as a stereo source into OS9; we could have been more helpful from the start if you mentioned the synths... please forgive us, you may have to sell the 2496 
Hahaha, it's all good.
I have the synths going into FX units then going to the mixer that goes to the card but sometimes I need to adjust volumes in post so I thought multitrack recording would be nifty, though recording one at a time into the card often gives rise to chopping up the sounds to rearrange them and then using them like that.
Additionally two sound cards is always useful to send stuff out of the computer through external FX units and then back into the computer.
I might buy a second sound card after this one arrives because of that reason though.
Hopefully the midi is much tighter on this card than those shitty usb to midi cables I have because they are terrible for syncing computers to play together.