Mod or replace?

[mjp200581]

I would like to improve my digital source components (CD transport and DAC) as I reckon they are now the weakest link in my system.
The question is do I simply replace them with superior units or try modding the existing units?
I'm currently using a Cambridge Audio CD6 player as a transport linked to Cambridge Audio DAC 3.
Is it worth modding either of these units?

 

[mjp200581]

Capacitor upgrade on Isomagic

Here is an update:
In the end I replaced the DAC 3 with a Cambridge Audio S700 Isomagic as this is reputed to be a superior design. Initial listening showed the S700 to have a slightly crisper cleaner presentation than the DAC3 but I was expecting more.
After a bit of reading around I decided to replace most of the capacitors on the circuit board as other users have reported significant benefits.
I used a mixture of Nichicon Fine Gold and Elna Cerafine electrolytics for the upgrade and I'm really glad I did as the sound quality has been improved dramatically!
I'm now looking for a Cambridge Audio discmagic transport to partner with the Isomagic since these units have the ability to 'clock lock' via a toslink cable.