As everyone else has said, don't put a really nice cartridge on the Dual...it's a waste...in fact, it is because I have a range of cartridges that stretch all the way from gimme AT CN3600's to Benz wood bodies that I have done a lot of experimenting with my Dual...I have even tried one of my MC cartridges on my 1218...
Let me tell you, that's a waste of time.
The cartridge mounting scheme leaves so much to be desired that there is no way you can solidly mount a cartridge in the headshell...and, with all the connections between the cartridge and the RCA plug you stick in your Rotel, well, it's almost amazing that any decent sound get through at all, in fact, I count ten such junctions, or solder joints, or switch contacts, etc., in my 1218....and, they are not all of the highest quality....
The Dual's mount doesn't give as rigid a mount as many cartridges need...now, there are some cartridges that work pretty well, but I found one of my MC's not to work well, where it has been just fine on a more rigid headshell scheme...a Grado Blue was OK, but the best so far has been a Stanton 681 with a Pickering D750 stylus...it really was much better than the Audio Technica AT3200E HOMC I tried...after that I decided that it would be a waste to put on anything even better...plus, it doesn't take a lot of effort to change the Pickering stylus for a Stanton 78 RPM one when I want to play 78's...yes, there are many Stanton/Pickering marriages that are possible....
I know there is a whole cult following around Duals...I like mine for what it is, but it is not in the league of almost all my other tables when it comes to ultimate fidelity...maybe after I replace the old tonearm wiring, and see if I can change the make/break muting switch to a grounding type mute the sound quality may go up a notch...but seeing as you are in England maybe you should look into a decent Rega...and you have to understand that I am not a Rega "fanboy"...but on your side of the pond they do present a decent budget alternative to other tables...and their arms (RB250/300 at least) will really let better cartridges, like your Goldring, be able to show you more of what they can do.
Now, I know I am going to hear from the Dual fanboys, but hey, I have one, my observations are based on what I have done, what I have heard, and in comparison to some of the midrange tables that I have on hand, such as my Yamaha PX-3. Micro Seki BL-51, Denon DP-45F, and my 1218 really can't swim in the same water resolution wise as those three...much less in comparison to my Linn...it does have a great sense of drive, has great speed stability, but is really held back by it's short tonearm without any real kind of VTA adjustment, a really, really crappy cartridge mount, and nearly 40 year old wiring with all it's contacts and connections...
So, don't expect a high-res machine from your Dual, but one that can play music, and quite satisfyingly so, and is a funky, fun piece of gear to play with.
Now, what LP's are you listening to?
It could be that the pressings you have listened to have just not been up to par and preventing you from hearing what may be on the same CD"s...
It is a different world!!!