Good on you for switching to Linux! What distro are you using? I’ve a little experience using Ubuntu Studio; it’s pretty solid, as far as Linux goes, for audio production.
However, as much as I love Linux, I find it lags far behind Windows and Mac for audio production.
At least I understand why you’re going for a hardware solution now!
OTOH, I’d suggest that the “something missing” feeling is probably one of these issues:
> An inadequate soundcard
> A home stereo amplifier
> Home stereo speakers
A hardware synthesizer will deal with the soundcard problem, but it won’t necessary sound good if your amplifier and speakers aren’t up to the task.
Moreover, you’ll find that the biases of general consumer hardware will lead to problems with your mixdowns. Consumer amplifiers and speakers are biased towards the midrange to make music sound ‘warmer’ and to bring out the voice in songs and soundtracks. For music production and mixing, you really want a frequency response that is as flat as possible – flat frequency responses are brutal to poorly mixed music, which is what you want: if you can make it sound balanced on monitors, it’s much more likely to sound balanced on reasonable consumer audio set-up.
You’ll also likely need a hardware mixer if you plan to go down the hardware synth route – you need to record the output from the synth somewhere.
Moreover, you’re going to need a midi controller – that synth is only capable of 8 note polyphony, so you’re going to need synthesised audio for the other tracks, which implies something to manage them all.
I’d still recommend a software synth option backed up with decent sound equipment and a more suitable operating system (Windows XP Home is all you need). You will notice a difference, and you will retain the flexibility of a computer setup. You can buy an ASIO/MIDI controller later and play the computer directly using that.