Re: Should I buy...
The Polaris is a more expensive american style synth with a more "solid" sound then the SIEL. I think a SIEL Opera 6 goes for 300ish euro and Polaris go in the direction of a 1000 euro.
The Opera 6 is the same as the DK600 and Siel KIWI, if you can find the last one go for that cause its just awesome how it sais KIWI in giant letters on the back (the story was that the KIWI was especially for the german market and there was already a synth called Banana so the SIEL ept. thought germans liked fruit names for their synthesizers)