Is my cartridge the problem?

Well, I wouldn't be too quick to get a new cartridge. That may not solve anything. One thing that CD's do very well, everything else being equal, is image. Especially compared to vinyl if your TT/arm/cartridge are not optimally set up. Even then its a good contest.

The critical things must be done properly, VTA (a biggy) VTF, anti skate, and cartridge alignment. You can get some fairly big changes by experimenting with VTA/VTF (by ear) once you have dialed in the manufacturers recommended set up.

Who ever said vinyl was an easy medium was blowing in your ear. Its not plug and play, but well done it can be excellent. Bear in mind there is a very good reason that folks who are into vinyl will pay big bucks for turntables and arms. They are not just rich and /or foolish. You can only expect so much out of a modest rig.

Get out you alignment tools, your arm level, your platter level, and your VTF guage and have at it! :-)

Here is a link to fine-tuning your table if you want some excellent tips.http://www.walkeraudio.com/fine_tuning_your_turntable.htm a Denon DL-103 cartridge might be worth looking into.I think the NAD PP-2 has a moving coil capability.

The cartridge is not the problem, it's the arm. Your tonearm is basically an entry level unit; although it may track the Denon 103 and other more expensive cartridges,it will not track them well enough to fully realize their potential.
Save your pennies and upgrade the table/tonearm. Look for a nice used combo. All of course IMO.