I love my dx.
I have it sampled in my mpc which is fine, but for a serious song coming straight from the real machine and manipulating it, sounds better imo, don't care to argue.
You can get midi conversion in a couple ways now too.
The machine swings nicely and even just badly mashing the buttons usually comes up with a nice pattern.
If I am not mistaken the 505, 707 and R8 are all just digital sample-based drum machines. Unless what you're after is their particular hardware UI or sequencers, there's not much sense in buying one. If you just want their sounds, you can go grab sample libraries for any of these machines much cheaper.
If you were talking about an 808 or a 909, then that's different... since those machines are analog and you can tweak the parameters of the sound in ways that samples can't fully capture. But 505/707/R8 is just playing back a sample and all you control is volume/accent. Which you can do on an MPC, or on any sampler plugin.
Unless you specifically want the hardware experience, my recommendation is to shop a few drum hit sample libraries, then invest time learning to use whatever sampler plugin floats your boat - can sculpt the sound a lot from there with additional filtering and effects, make them your own.
James, if you want the New Order sound, the Oberheim DMX is what you want. For a "cheap 'n easy" solution, you can simply download free samples of the DMX, load them into Logic's UltraBeat, and arrange them in typical '80s patterns.
P.S. The LinnDrum is one of the easiest drum machines to use