Meridian 508-20 to 508-24 Upgrade

I am considering the upgrade to the 24 bit status and was wondering if anyone who had this done could provide feedback on the upgrade. Specifically are there noticable improvements in the sound and what was the experience with Meridian (turnaround time). Thanks for your help.
I can highly recommend the Meridian upgrade (as a Meridian improvement). I have a Meridian DAC that I upgraded from 1-bit to 20-bit to 24-bit. I chose to do this after hearing an Audiomat 24-bit DAC kill my 20-bit Meridian. I called Meridian America and talked to a tech about what I heard. He reassured me that it was as much due to 24-bit vs. 20-bit as it did Meridian vs. Audiomat. I chose to upgrade, not switch, because it was economically a better deal. The upgrade was all that was advertised. I don't regret it for a moment. Give Meridian America a call and get the details of the improvment that will be heard even with 16-bit CDs. The 24-bit improvement were quieter and blacker background. Better base control and more open high end. Better sound stage and a bit more detail. Again, give Meridian America a call and get the explanation as to why (it sold me on it). BTW, I sent the unit in directly (no dealer) and found Meridian a joy to work with (notify you when they get it and prompt with return).
My 508.20 was updated by Meridian at their expense after I returned my unit a second time for a faulty drive mechanism. The upgrade is definitely worth considering. The .24 has better highs and lows, sounds more open, and is more evenly balanced top to bottom. I also percieve more detail, and a greater freedom from congestion on complex passages. The .20 is a little slower and thicker sounding, where as the .24 has better pace and agility. The only indication from the outside that you have an upgraded unit is a sticker on the back that says '24 bit DACs installed'. Tom
Hey guys...What do you think of upgrading a 506-18 to 24 (would it be huge) and does this upgrade offer up-sampling? Please advise.