NAD 3130, should I keep it?

I ask because I just bought some Sennheiser 580 headphones, and am about to buy a good headphone amp. I believe the NAD will still have some bearing on the overall sound since the headphone amp connects to the tape loop of the NAD.

The 3130 is about 15 years old or so, and works great, but will it have deteriorated in quality by now or stayed the same? I'm no audiophile, but it sounds fine to me. Warm and lots of bass. In other words, is my source good or bad? I've been advised to check my source isn't 'crap'.

Also, my CD player, which is all that I currently use with the 3130 is about the same age, a Marantz CD 65 mkll. Is that good, or do I need to upgrade, say, to a current NAD amp? I just have no idea what sonic differences I'd get with newer equipment. My personal taste in sound is pretty much what I'm getting now only I would like it crisper and more alive. I don't know whether a headphone amp will be all I need to upgrade to achieve this, or other stuff as well. Thanks in advance. :)
Roman- If you run the headphone amp from the tape loop, the NAD will have no impact on the sound. But you would certainly benefit from a more current CDP. Do some searches in the archives, but you could buy, for example, Sony 7000 or Pioneer Elite DV-05 for about $250-300 that will be a dramatic improvement.
Thanks for your reply Swampwalker. Actually, I found out today how weak my CDP actually is. I heard a marantz 6000SE and it was fantastic. Really crisp and alive. Buying it tomorrow for £220.:)