CAL Icon vs. Cambridge D500SE vs. DAC

I've got the urge to try and improve my source, but on a limited budget. Today, I have an AMC 8B source connected to a low-power tube integrated. I'm hoping to do a minor upgrade in my source component. There are two options I'm considering. One is to incrementally upgrade to a 'better' source and the second is attaching an external tube DAC.

The new sources I'm considering is an older cd player versus newer cd player. I've been looking at the California Audio Labs Icon MKII and the Cambridge Audio D500SE... both have good reviews, but the CAL is quite a bit older. Is a good 10-year old CD player equal to a good CD player today?

Second question is, would I get more out of using my current source and attaching something like an ART DI/O DAC? Considering the relatively low budget of the sources above, I would appreciate any feedback.

The answer to your first question is "yes" in my opinion. The CAL Icon Mk II is a fine CDP. Warm and musical w/a strong bass presentation, although not so tight. The hand-trimmed DAC's are what make this player very fine. At the moment one of my CDP's is an older high-end (1986) NEC which sounds great. Haven't heard the Cambridge for an extended length of time, so unable to comment. Good Luck on your path to sonic bliss!
I vote for the Cal---BUT---I'd look for one with the HDCD decoding and Power Boss upgrade. One well built player. But---another but!---it is not as transparent as the Cal CL15 or some of the newer players in this price range. I owned the Cal Icon, the CL15 and a variety of NAD's and Marantz so called giant killers over the years. I always prefered the Cal Icon w/hdcd and the power boss upgrade. It just sounded so musical. So much for my 2-cents!
You should really try the Nixon Dackit. Don't know how to say it with less emphassis... with my current transport, the Nixon blows away the CAL Delta/Alpha... ok there.