A couple of weeks ago I finished making a soundset for the TAL Bassline 101. You know what I discovered? That you don't need much more than something like that. A basic synthesizer with basic functionality such as polyphony, envelopes and filter is enough to do pretty much what most synth-heads need. Ever. If you already own a DAW you probably have more than you'll ever need.
No one needs another synthesizer. But I love meeting new synths and plugs and see what kind of connection you will get with them. Diva and Omnisphere are at this point virtually connected to my spine. My last hardware purchase was the Elektron Digitakt - which was an insane impulse buy, since I already own two(!) Analog Rytms and theoretically they cover way more ground than the Digitakt. But the Digitakt is absolutely fantastic and totally kicks ass when it comes to workflow and is now responsible for one of the ARs to be sold on eBay.
You never know when you've stuck gold with something new until you've worked with it, and for some time.
/C