A CAT5000 running catOS is identical to a 6500 from an administrative standpoint and is definitely a good practice. The 6000 just has more hardware (bigger back plane, higher density (can have more blades, and can have more ports per blade).
I 100% agree that a 5000 is a great piece of lab eqiupment for learning the device.
But something to consider - the 6000 is definitely a big piece of equipment and if it can affect a large group of people, I'd highly recommend you get some detailed training for the CatOS. A good class would be the BCMSN class (Building Cisco Multi-Switched Networks). It focuses on the 5000/6000 switches.
The only drawback is that the BCMSN is now focusing on the IOS version, not the CATOS version. But this is the direction Cisco says they are going as the CatOS will be extinct in coming years.
If you can't afford formal training, or want to stick to learning the CatOS, then I'd suggest finding a an older BCMSN book (from probably
2002 or 2003, for CCNP test # 640-504). This should cover most of what you'd need to learn (and you could practice on a Cat5000.
Ryan