The goal is to have fun..you can get some even with pc speakers.monitors are expensive and are mandatory if you wanna get "pro" results,but if you are starting,don't bother.you'll change them when you feel the need.
You first need to get sound in your headphones...plug them in card's phones plug and try to get sound with sonar.when done,you'll naturally get sound with speakers.
Is your headphone stereo minijack? If so,just use the adapter to get jack.they exist as stereo and are cheap so just get a stereo one.

Don't be too frustrated.all is about having fun

Error posting....sorry

guigz2000
The goal is to have fun..you can get some even with pc speakers.monitors are expensive and are mandatory if you wanna get "pro" results,but if you are starting,don't bother.you'll change them when you feel the need.
You first need to get sound in your headphones...plug them in card's phones plug and try to get sound with sonar.when done,you'll naturally get sound with speakers.
Is your headphone stereo minijack? If so,just use the adapter to get jack.they exist as stereo and are cheap so just get a stereo one.

Don't be too frustrated.all is about having fun

ok thanks a lot. Fun yes, thanks for reminding me!

By the way since you're not recording anything acoustic and the inputs on your Roland are free you can actually hook up the green mini jack output of your old on-board soundcard to the inputs of the Roland and use its monitoring function to let the sound pass through to the speakers (or headphones). This has the benefit that you can continue to use your "regular" soundcard for all normal Windows based stuff such as Skype (plug the mic into your normal card as you always did!) and YouTube, and can keep the Roland for Sonar exclusively.

Oh and yes two outputs on your soundcard means you get stereo sound. Each monitor speaker is hooked up with its individual "mono" cable. This is the case for all professional and even most consumer speakers. Computer speakers and headphones are the exception in that they use a single plug with a dual cable. Stereo really is twice mono, the effect is in the source material being different for each channel.

Sanderxpander
By the way since you're not recording anything acoustic and the inputs on your Roland are free you can actually hook up the green mini jack output of your old on-board soundcard to the inputs of the Roland and use its monitoring function to let the sound pass through to the speakers (or headphones). This has the benefit that you can continue to use your "regular" soundcard for all normal Windows based stuff such as Skype (plug the mic into your normal card as you always did!) and YouTube, and can keep the Roland for Sonar exclusively.

Thanks, I like the sound of that! (no pun itended)
 
And thanks for clarifying the stereo being 2 x mono.
 
thanks for your help

Sanderxpander
By the way since you're not recording anything acoustic and the inputs on your Roland are free you can actually hook up the green mini jack output of your old on-board soundcard to the inputs of the Roland and use its monitoring function to let the sound pass through to the speakers (or headphones). This has the benefit that you can continue to use your "regular" soundcard for all normal Windows based stuff such as Skype (plug the mic into your normal card as you always did!) and YouTube, and can keep the Roland for Sonar exclusively.

Hi Sanderxpander,
 
I got sorted with my sound card and speakers,  but at the moment I have to use two sets of speakers; one for Sonar via the interface and one for all other sound.
 
Just to clarify, when you said the above, did you mean using one of these cables?:
http://www.amazon.co.uk/3-5mm-Stereo-6-35mm-Audio-Cable/dp/B0034DSUMK/ref=sr_1_7?ie=UTF8&qid=1383691664&sr=8-7&keywords=mini+jack+to+twin+jack
 
...from the mini jack port on the PC to the Input 1 and Input 2 (for mics) on the from of the Duo Capture?

 
 
If so I will order the cable, thanks