It tend to be difficult in a lab environemnt to verify the results of QOS policies applied to routers and switches. The reason being is that some things, like delay, are very difficult to simulate. When I took my QOS class through Global Knowledge they were able to simulate things like delay by using a Cisco Pagent which is a modified router running a version of IOS not available to the general public.
As for a lab structure. I would go with at least 1 ISR router and 1 new style switch (3560 or above). These aren't cheap though and for the most part, the general concepts can be completed on lower end devices. If you are able to get your hands on some IP phones as well, that would be advisable for your lab. However, you know as well as I do, to pass this type of test, you probably don't have to havr the lab. By this point in your studies (already passed the CCNP) most of the commands should be very recognizable to you. The lab would be more for verification of the concepts you learned and practice. You could pass without it, I did.
As for the CCVP vs. CCIP track, I choose to answer with another question...Do you plan on ever going for your CCIE (Routing and Switching). If so, go with the CCIP track as it encompasses QOS, and BGP which are cornerstones of thew CCIE . It also has MPLS whch will most likely soon be a part as well. If you ever want to go CCIE for voice, well than that choice should be obvious with the CCVP.
Good luck, I think QOS is a great foundation to your networking skills and is one of the current hot topics in the networking world and isn't likely to die down anytime soon.
