I have an HK930 and use it fairly often as part of a classroom teaching system (with a pair of Dynaco A25s) and as a nostalgia piece--a very long time ago, I used to sell them. It was a standout in its time and still gives very good sound for parts and a design that old.
One upgrade option we have with this unit is replacing aging parts, especially capacitors and perhaps diodes and some resistors. I have no doubt that its sound would be improved that way, but unless I did the work myself the cost would soon run into the territory of a used NAD C320BEE.
We also have the C320BEE at home, so I can compare from experience.
The C320BEE does sound better to my ears. It doesn't have the bass weight and control provided by the 930's dual power supplies, but it is more detailed and transparent. If you replace the stock jumpers on the NAD's back panel (something you should also do for your 930), the sound loses forwardness and edge and the harmonic balance gets better.
I also have a pair of Triangle speakers, the TItus ES, running off a tube integrated, an Audio Space AS-3i. This system is a big step up in refinement from the NAD, by the way, and a variant on it may be possible at close to your budget, with the Triangle Comète for example, and second-hand prices. However that is really another question.
The most reasonable improvement path might be this: find a used C320BEE or C325BEE and a pair of Triangles. Replace the jumpers all round, speakers too. (I like single-crystal copper for this.) Have the 930's tuner aligned if it hasn't been done already. Use quality interconnects and speaker cables--Atlas Equator and Audioquest Type 4 would be my budget picks but you will find many other good ideas here too.
Finally, if you don't have one already, look out for a good digital interconnect cable, an Apogee Wyde Eye at least, and make sure its length is 1.5 metres. I know, there has been controversy over the length issue, but the cable was a Stereophile recommendation all the same and I have tested different lengths myself.
If, after having done all that, you don't feel the improvement is sufficient, you can resell the NAD and put the proceeds towards a tube integrated!
One upgrade option we have with this unit is replacing aging parts, especially capacitors and perhaps diodes and some resistors. I have no doubt that its sound would be improved that way, but unless I did the work myself the cost would soon run into the territory of a used NAD C320BEE.
We also have the C320BEE at home, so I can compare from experience.
The C320BEE does sound better to my ears. It doesn't have the bass weight and control provided by the 930's dual power supplies, but it is more detailed and transparent. If you replace the stock jumpers on the NAD's back panel (something you should also do for your 930), the sound loses forwardness and edge and the harmonic balance gets better.
I also have a pair of Triangle speakers, the TItus ES, running off a tube integrated, an Audio Space AS-3i. This system is a big step up in refinement from the NAD, by the way, and a variant on it may be possible at close to your budget, with the Triangle Comète for example, and second-hand prices. However that is really another question.
The most reasonable improvement path might be this: find a used C320BEE or C325BEE and a pair of Triangles. Replace the jumpers all round, speakers too. (I like single-crystal copper for this.) Have the 930's tuner aligned if it hasn't been done already. Use quality interconnects and speaker cables--Atlas Equator and Audioquest Type 4 would be my budget picks but you will find many other good ideas here too.
Finally, if you don't have one already, look out for a good digital interconnect cable, an Apogee Wyde Eye at least, and make sure its length is 1.5 metres. I know, there has been controversy over the length issue, but the cable was a Stereophile recommendation all the same and I have tested different lengths myself.
If, after having done all that, you don't feel the improvement is sufficient, you can resell the NAD and put the proceeds towards a tube integrated!