Will I notice the differance?

I own the Rega Apollo, and it is by far the most beautiful sounding cdp I've ever owned (I've also had the Planet 2000, the Ah! Njoe Tjoeb 4000 with upsampler, etc.)
The next batch of Apollos won't be here until beginning of March. So, save your pennies!
The Apollo does not make older cd's sound horrible; conversely, I found it makes them sound terrific. Whereas I could hardly listen to them before with the Planet 2000, with the Apollo they "come to life" and make it very pleasant to listen to them. The Apollo does not highlight the weaknesses of the older cds, but rather is able to extract more information from those discs and make them sound closer to a new recording.
The Apollo uses 20 meg of memory and 32 bit processing. One can easily hear the improvement in technology over standard 24 bit systems. Try, if at all possible, to audition one.
You can see my initial review of the unit on Audio Assylum:

http://www.audioasylum.com/cgi/m.pl?forum=digital&n=113988&review=1

You should be able to do well now in your selection. There are used Panets and Jupiters coming along since the people are upgrading to the Apollo. If you can stretch your budget, I would say don't hesitate to go for the top - the Apollo. But, even a used Planet 2000 would be a nice improvement. I had NO IDEA what I was missing in the music until I compared the them.

Get a used Rega Planet 2000 in the $500 range and spend the rest on music or new interconnects to hook up your cd player. You'll be very happy.

Thanks guys for the responses.

OK peeps, I bought a Arcam CD73. To answer my own question, yes, I noticed a HUGE differance. I am happy now. Very happy!

I used to have the CAL Icon II Boss and really enjoyed it. Not too detailed, but relaxed with no glare or tizz. I traded it for a Meridian 508.24 and did not think it was any better. This was around 1997-8. The CAL was very reliable and never had any problems. I think for around $5-600 it's a bargain.