How can I start to change the system?

First of all, I must to say that I don't speak English well. So please keep that in mind. I live in Lima, Peru.

I have the following:

DVD player Rotel RDV 995 (working like an audio transport)
One Coral Cable interconnect (working like a digital cable)
DAC California Audio Labs Sigma II
AudioQuest Jaguar Interconnect
Integrated Amp Rotel RA01
AudioQuest CV6 Speaker Cables
Triangle Comette 202 Speakers

I enjoy this system a lot but I would like improve it. I was thinking about buying an tube amplifier and I wonder if I must buy another component before.

Any opinion?