I never thought I'd fill up a second chassis either - but I did!
If you'll ever need more than your 8 current Preamps - I would consider investing in a second SCA rack - and even add a T15 or something cheap. I'm not sure if the DI gets the package discount - but the T15 will...
You'll probably want some J99's at some point - and you'll need another rack then
With the package discounts - it ends up being surprisingly affordable (probably about the same as you buying an external PSU and some sort of enclosure for the single DI anyway - but then you'll have 7 open slots for future expansion!)
Edit - The DI doesn't quality for the package discount - but the $79 T15 does qualify for the $297 SCA Package Discount! So, $478 for another Chassis, PSU, DI kit and T15 kit vs probably like $200 for a generic 1RU chassis and PSU (and still need the $79 SCA DI Kit, and some fabricating to get it mounted, too!). AND you'll have a T15 and 6 free slots for future expansion. Seems like a no brainer to me...
Just trying to get by...
Randy V.
8x A12; 4x N72; 2x J99; 2x C84