great brass oscillator preset

Your Korg is limited (I think - I'm not real familiar with that kybd) to the samples contained in its internal ROM memory. All you can do is edit the filters and fx that are applied to that sample. If the keyboard has RAM memory where you can load in your own samples, then you'll have to see what formats are supported and what samples are available in those formats.

What it sounds like you might be after, though, is a VST instrument or "softsynth" which is a piece of software that lives on you computer and is called up within Sonar and triggered via MIDI. There are plenty of good brass sample libraries in VST form on the market. Some are better for classical and others are better for pop/R&B type music. Google brass VSTi and you'll get started on your search. If you'll tell us what type of music you're working on we can recommend specific libraries.

most of the keyboards that are in the low to mid price range has mediocre sounding brass samples.

Your best bet for quality brass will be the VST's that specialize in brass sections...and the good ones will cost a bit.

If you want something that sounds real.... it's your choice.

Obviously what you have now sounds cheesy, that;s why you're looking for a better sound.

To me $3k is big bucks, but you can land a nice horn VST for a whole lot less than that. Realistically I think you're probably looking at around $500 to get something decent that doesn't sound like a synthesizer trying to imitate a horn section.

What you ultimately pay will be determined by the sound you're willing to pay for.

Kontakt 4 has some decent horns, so does GPO in the lower price range under $500.... but you have to work them to get them sounding real.

I have heard people talk highly of these  >>  Chris Hein Horns   but buying the complete sets will be pricey with the bundle at $1250.oo....... still way cheaper than a new keyboard at $3k....

You get what you pay for.