Hand me down audio equip- upgrade advice


First off, this might be my first post, but I’ve been admiring the Audiogon community for a while now. There’s a ton of helpful information that a lot of you have shared, and I appreciate that!

I’m lucky enough to have a boss who’s big into audio equipment, and handed down some of his older gear to me:

Benchmark DAC2 D
Classe CP-700
NuForce Reference 18 monoblocks
KEF 103/3 Reference w/ Kef Kube equalizer
Vandersteen v2w sub

I ended up having to refoam the KEF’s, but I have to say they are a great speaker! I’ve been enjoying this setup for about a year now, and want to explore some newer speaker options- preferably a floor standing full range variety. At this point, I’m fairly overwhelmed with the options out there- and looking for some wisdom.

I’d like to keep my first upgrade under $1500, with some wiggle room. I’ve been drooling over some Sonus Faber’s, but alas, I’m not ready to bite the bullet on anything in that price range (used, of course). KEF has plenty of lower to medium priced speakers, but I’d like to explore other avenues.

Thanks in advance
rillerr
First you need to find out what your boss is going to hand you down next. If nothing, ask your boss what you should get, and pick up some brownie points. Sorry!
You could probably sell the Classe, NuForce, and KEF for about enough to get a Raven Blackhawk and Tekton Double Impacts. Depending on what you can get for them this could be anywhere from a little cash in your pocket to costing about what you're planning now. Only instead of baby steps this would be a big leap forward. Bigger sound stage, plenty of bass, and a rig that will sound great with all your range of music.
OP, 

Someone with better hands did the refoam and ferrofluid. I did the recap of crossover and the Kube. If you have the time and the confidence (well, you did the refoam), I think you can do the ferrofluid as well. 
You have already identified that you like your set up - the Kef is a great speaker, however you want to expand the soundstage. 

In order to maximize your existing set up and achieve a  better soundstage with your max budget of $1,500 the best path forward (as others have pointed out) is investing in upgrading what you already have by:
1. Adding another Vandy Sub.- used - Your adding another L&R diver to the kefs, with a dedicated power source. Expands the Mid/ Low range.
2. Investing in Power delivery. - used, Think of it as another component to your system. Will add detail,Imaging, Depth Texture - maximize your amp preamp performance. 
3. Look into upgrading your crossovers/recap etc.  - Cleaner, efficient presentation. 
And I don't even think your budget is going to cover that, but its a solid move towards getting to be where you want to be.

Investing in different speakers in your budget is a lateral/backwards move that will not solve your issues. You want to make investments that move you forward towards achieving your goals. 

Good Luck
Easy upgrade. I just sold my Monitor Audio silver 300 current model for $1299. They are a fantastic value with excellent bottom end. That would leave a few dollars for a decent set of cables, if needed. I liked them so much I upgraded to the gold 300s. Good luck. Ridiculous $$ spent on electrical solutions are frivolous at your stage of the game. Speakers and DaCS will provide a noteworthy improvement you will always hear the difference every day.