You've come to the right place! I have BOTH of these receivers in mint condition and they're both nearly identical in terms of performance and specs. I wanted a D1s SO badly for years because it was the elusive Pioneer that my dad didn't buy and he instead opted for a more affordable VSX 9900s. Now that I own both and they both work flawlessly that you losing out on the D1s isn't the end of the world. The 9900s will easily hold its own against its slightly bigger brother. The main differences between the D1s that I found nice was it used a flip down panel to hide the surround controls including the volume controls for the centre and rear channels whereas the 9900s requires you to use the remote to do the same adjustment. The D1s Input selector buttons are machined aluminum vs. plastic on the 9900, the display on the D1s shows individual bars for each channel that is takes up half of the front panel display vs. a condensed version on the 9900s that only occupies just a quarter of the display (on the left side). The D1s b/c of the fold down panel gives it a cleaner front as well.
In terms of acoustics you'd be hard pressed to tell the difference. The D1s sports more power but as far as listening volumes are concerned I have two identical setups side by side in my basement and doing A/B testing I can't tell the difference. Both receivers have the same THD figures, use basically the same power supply and even weigh nearly the same. They both also use Pioneer's non switching amp design and they run hot hot hot so heat degradation of components are a reality on these things.
As king bubba has indicated finding a remote for either of these receivers to enable all functionality will be difficult at best. Trust me I've looked for a hell of a long time and the closest thing I found is a new CU-AV200 learning remote from Pioneer that was a fancy glorified LCD remote for this receiver. It controls a LOT on these receivers but it doesn't control everything like the factory included remote would. If you intent to only ever use it on stereo mode and need a basic remote then any older Pioneer receiver remote (including even the touch LCD remotes) will work with either receiver. You're only really using the power button, input function button, volume and maybe mute which almost ALL Pioneer receiver remotes have.
If you can't find yourself a decent deal on a 9900s or a D1S consider looking at Pioneer VSX-d901S or a VSX-d902s. They were updated copies of the original 9900/9900s and were just as good if not exactly the same unit.
Hope that helps!
