I need a USB interface that is compatible with Sonar 3X so I can mix in 5.1  Any suggestions?
 
Speaker set up?
 
Use all the same power speakers? Most power speakers are sold in pairs.What about a powered center speaker?

 
 
If you want to mix in 5.1 surround you will need an interface with six analog outputs (unless you have digital powered):  A) 2 for right and left (mains); B)  2 L & R rear satellite monitors;  C) 1 for the center satellite monitor; 4) 1 more for a subwoofer (optional).
 
You could use any speakers, I guess, but if you are going to mix then I suggest reference monitors (which are sold individually).  As for USB interfaces, here are a few from cheap to expensive to much more expensive:  Behringer FCA610 ($200); TASCAM US-1800 ($200); Steinberg UR28M ($400); Roland Octa-Capture ($600); Roland Studio-Capture ($1000); Focusrite Scarlett 18i20 ($500); MOTU 828x ($850); MOTU 896mk3 Hybrid ($1000); MOTU 1248 ($1500); RME Fireface UC ($1400); RME Fireface UCX ($1600);RME Fireface 802 ($2000); and then there are those that are over $2000 from makers such as Antelope Audio, Prism Sound and Lynx (which may require additional hardware), just to name a few.  Some of the above mentioned interfaces have more than enough features for your needs, but I did list those that meet the minimum as well (eg, six analog outs). 
 
Kind regards,
 
Living Room Rocker

What's your budget?
 
You could easily spend tens of thousands on this

It looks I have a lot of good choices as far as a Audio Interface working with Sonar. The M-Track Eight from M-Audio is coming out soon too. It looks good.
 
It is the 5.1 monitoring system that is sticky. I have 2 powered Mackies for fronts and a Tannoy Sub which I have been using to mix in stereo. I filmed a concert while using Edius as my video editor. The stereo mix is done.
 
Sweetwater Music advised me (with my budget restrictions) to purchase all the same powered speakers for fronts and rears while using the same sub. (Not needing a Audiophile Quality Surround Level Controller) I was looking to buy 2 sets of the M-Audio AV-40s. But I will need a powered center speaker and most active speakers only sell in pairs. Any suggestions?

Jgillilan
But I will need a powered center speaker and most active speakers only sell in pairs. Any suggestions?

Hi Jeff, I am not sure what size (or type of) speakers you would be referring to but you can go into any music store and purchase a single monitor.  They are not sold in pairs but individually, unless you are purchasing small ones like 3".  It is only preferred to buy in pairs (just as Sweetwater suggested, the same monitors).
 
Kind regards,
 
Living Room Rocker
 
P.S.  I guess my edit to my first response did not take, but...  Welcome to the Cakewalk forums, Jeff.

Give me some examples if have you time. I want them to be all the same, so we are talking 5 speakers. Did you check out the M-Audio AV-40s. That is my example of what I need.

I surely can give you a ton and more examples.  In fact, there are so many monitor/speakers available they can fill a catalog in several volumes.  I did look at the AV-40s which have a 4" driver.  That is small for a reference monitor and I can't imagine the limitation on the frequency range they provide, but I am sure it is limited in the mid range which is the most important range when it comes to mixing.  Further, I would not depend on a subwoofer for the low end mixing either.  However, I understand budget limitations and they must be taken into consideration, particularly when it comes to a multiple monitor setup.  I will check things out and get back to you.
 
Kind regards,
 
Living Room Rocker

Thanks for your response. 1/2 ton of examples would even be great! I am anxiously awaiting your suggestions!

Hi Jeff, I have a link to Sweetwater's list of active/powered monitors:  http://www.sweetwater.com/c405--Active_Monitors/pn1
As you will note, the majority of monitors are sold individually ("ea.").  However, as I noted previously, small "woofer" speakers are sold in pairs.  I did see one or two 5" monitors listed in pairs.  The other factor in those sold in pairs are the value of the monitors.  The lowered end type made by Samson, Behringer, Alesis and, yes, M-audio are often sold in pairs.  These types would be most often out of consideration for mixing.  This is just to support my statement that you can buy monitors individually (not any specific brand).
 
I suggest you purchase three more Mackies to match those you already have.  What model of Mackies to you currently have?
 
Kind regards,
 
Living Room Rocker

My Mackies are almost 10 years old. They don't make them anymore. After reading your lastest response and doing some of my own research, I have come to the conclusion that I need to put some money together and do this right.
 
I think in the future somebody will introduce a USB or Firewire Amp with outputs to mix in 5.1 & 7.1 that will work with your DAW. I was being naive thinking I could buy 3 more powered speakers to work with my Mackies and Tannoy sub. Thanks for all your help.