I'm looking for a good VST for my MIDI bass tracks.
I'd prefer electric & acoustic bass.
I have Dimension Pro but it is limited.

Try the Cakewalk Studio Instruments bass that comes with SONAR - it's not as versatile as a lot of bass synths, but it's not at all bad (I've been using it quite a bit lately, originally intended just as a scratch track, but quite a lot have stayed).  Adding some warmth afterwards, like the Pro Channel Saturation Knob, an amp sim like TH3 or even the venerable Cakewalk Amp Sim makes a lot of difference.

I agree about SI Bass.

I use it a lot as for scratch track to replace with real bass later.

Several times it has stayed on the finished track.

I particularly like the Jazz bass sound. As KPerry said, a lot can be done with it by adding Sat Knob, compressor, Amp Sim, etc..

I have that but I'm looking for a high-quality dedicated bass VST.

Cakewalk Studio Instruments bass:
 
High quality - Check
Dedicated Bass vsti - Check
 
So what exactly are you looking for?
 
Why do you think Dim Pro is limited?

I've been using Spectrasonics Trillian for quite a while now.  I know that there are a ton of others, but I don't use them so I can't recommend them.

kontakt makes a few good one (J bass, Rick, exc) but im with the others, a lot can be done with cakewalks SI Bass.
I use it still quite a bit.
listen to the bass on this track right here....
https://soundcloud.com/charlie-roy/in-your-face
its not hard to identify the bass in this track as I believe it stands out a lot. (the grit)
that's Cakewalk SI Bass with some plug ins and saturation. its very useful.

Yes, I just bought the Kontakt Jay-Bass for $69.
I wanted to get Trillian but its beyond my budget right now at $300.
 

Take a look/listen to the Gibson Bass Collection Rapture Pro/Rapture Session expansion that Craig Anderton put together. Very nice. Not expensive. Lots of different tones.
 
https://www.cakewalk.com/Support/Knowledge-Base/2007013448/Gibson-Bass-Collection-Expansion-Pack
 
For an acoustic bass, the CoreBass Pear upright from Orange Tree Samples is killer.
 
https://www.orangetreesamples.com/products/corebass-pear
 

Trillian is definitely worth checking out for a dedicated bass VST. It has electrics, acoustics, uprights and synths and is very versatile.