Ehrlund Pre:
I was expecting to just use the EBS and send back the Ehrlund preamp but I did actually think it was worth it in the end. It brings up the signal very cleanly of the Ehrlund and it only has one job and I think it is good at what it does! I didn't think the EBS did quite the same job as well just from that point of view. Obviously the EBS does many things the Ehrlund preamp can't.
In terms of rig changes:
As an amp I had a GK MB150s with extension that I'm now trying to sell. I just couldn't hear the detail that the Ehrlund was delivering so it seemed like it was wasted on that rig. Also I found on that rig I'd get feedback with the Ehrlund without too much volume.
I now have a Barefaced audio Super Midget. It has a tweeter and is FRFR full range flat response 600w and silly loud for its size and weight. It's pretty much a studio monitor that is capable of behaving like a bass amp if you ask it to, but louder.
The EQ on the EBS gets me most of the way to where I want to be and I also find I scoop out more mid with my bass amp head to end up where I want to be especially in terms of sweetening the cab. I don't have experience with many heads but I'm using a GR bass one 800w. I'd say the GR bass is transparent unless you ask for something from it then you can have it! That setup is insanely loud and I believe it to be very versatile. I'm not sure which way I have the phase set but I get feedback if I go the other way so I stay where ever it is! I don't know if its just my bass or my EQ settings or Super midget wizardry but I can get it silly loud without feedback if my phase switch is in the right setting. I really can't imagine ever needing more volume on an upright gig. I do however have the realist as a backup as I have heard some people find the Ehrlund is to feedback prone for them. I actually have not had that problem myself with the super midget and I've been letting it rip! I run both pickups through a stereo jack then split them on the floor. I'm not crazy about having a millions leads and stuff all over my bass so this cleaned things up for me.
I also had a slightly maverick approach with the Ehrlund in terms of how I fitted it. I use an adapter from the male jack into a female jack then take it with jack cable down to the preamp. Technically you are not supposed to do this. I took several samples and I couldn't hear a perceivable difference if the Ehrlund went through a decent shortish jack before it hit the preamp or it went straight from their cable. I didn't want the preamp attached to my bass and I didn't feel I was losing anything sonically perceivable.
For you there might be cheaper/ better/ simpler ways to get where you want so I guess I'd advise you to try things hopefully with the option of returning them if they don't work for you. All I know is where I am I like and I think it was expensive and not the simplest set up ever but definitely worth it!