Another good budget choice would be the Steinberg UR-22. I use it, and being a hobbyist it is all I need and I have no problems with it. It's a USB.

I need 8 inputs because I record my band, live, all the time, and it takes 8 channels. I dont need that right now, my other machine, an older Windows XP system, has the nice delta card. Its fine for recording but doesnt have the power to mix. So, I mix on a newer, powerful Windows 7 machine. Its the Windows 7 machine that is using ASIO4ALL or MME to interface with a crappy, very low budget Soundblaster card.
 
Are you guys suggesting that I am getting an inaccurate playback if I use MME? Or even ASIO4ALL?
 
or that I'll get a better, "more true" playback with a FocusRite USB interface?

Maybe you should consider the Line6 UX1. Although it's primarily aimed at guitarists and has inputs that you don't need, it's known to work well with Sonar and it now seems to be available for under $200.
 
http://line6.com/podstudioux1/

so you want ASIO and to record 8 channels for under $200? 
If you want to record 8 channels at once and dump it into your daw, get a zoom R16.
I use Focusrite products and they are good for the money.

Which model of Audigy card do your Have? I have the Audigy II and there are windows 7 drivers for it. It is a PCI card with a breakout front panel and I just tested it last night and was surprised to find it works way better now than it did form me under XP 32 bit. There are no windows 8 drivers but it is possible the W 7 driver will work. Don't ever use asio4all. been there done that, it will be worse. Asio4all will work with the odd interface that doesn't come with drivers but in my experience it is not a stable driver. It is a WDM driver anyhow and not asio. 
 
Read this thread I'm running and go to page 2 to read about the Sound Blaster results.
http://forum.cakewalk.com/Lets-all-TEST-our-Interface-driver-for-offset-m3178396.aspx
 
And asking about interfaces will get you a dozen "opinions" all based on what the person owns. Please don't shop that way. You need to make your own decision based on what you need here's a blurb I made about looking at interfaces; 
http://www.cactusmusic.ca/Articles/Johns%20Audio%20Interface%20blurb.rtf
 
But for now my guess is the Audigy will work IF there are ASIO drivers. It is a huge waist of time to use on board audio and mme drivers as I have found with the loop back test. WDM and MME mode are plagued with timing issues. Dropouts, and latency that is unmanageable. 
Sonar = ASIO
no other option is a good option. 

I'm using the Focusrite Scarlett 6i6 and I am very happy with it

 
I just found this, and it claims to have ASIO drivers, and its onsale at amazon for 50 bucks.

http://us.creative.com/p/...ound-blaster-audigy-rx
 
I have its little brother, which sounds fine, my only problem was I worried that it did not support ASIO (it doesnt, but the above one, does)
 
is there any reason why I shouldnt try this?

You may have not looked in the right place for the drivers. Only new products are on the Creative Worlwide site, and there are no links that work directly from the home page, You have to type in your model number to Google which will show results for the support.creative site for legacy drivers.  here is where my drivers are found. 
http://support.creative.com/Products/ProductDetails.aspx?prodID=149&prodName=Audigy%202
 
And ya ya ya, Focusrite have real good drivers I also use a 6i6. I see no point in buying a Scarlett solo or 2i2 if your only mixing and you can find the asio drivers for what you have and it works fine. 
The best bang fore the buck for input count is Tascam if you need 8 or more inputs.  
 
 

Just to clarify to others, the OP is a bit misleading (especially the title), since the OP only requires mixing capability on a Win7 machine with a SoundBlaster card. I am not convinced that he does not already have what he needs to mix, since latency and driver mode are not as critical for mixing.
 
To the OP, some folks mix with 2048 samples, and this is not an issue, since everything plays back synched (just delayed in starting/stopping the transport). As long as good drivers do exist, playback is easily "doable." Your computer has the processing power and playback capability, is more getting it setup to use. "ASIO drivers" are not paramount in this case, but well-written drivers are (what we are trying to help you with).
 
As you said you have a recording setup and only require mixing, can you give us what model the card is that you have now? The "Device Manager" if you hit the Windows button and type this will give you the details if needed.

Cactus Music
 
But for now my guess is the Audigy will work IF there are ASIO drivers. It is a huge waist of time to use on board audio and mme drivers as I have found with the loop back test. WDM and MME mode are plagued with timing issues. Dropouts, and latency that is unmanageable. 
Sonar = ASIO
no other option is a good option. 

Finally I get why ASIO! thanks!
I just updated my Lexicon Alpha ($50.00) drivers that now are supporting the ASIO format, my slight timing issues are now gone! But on some old tracks they seem to be playing really slow. I think if I setup a new project file and adjust the timing then import the wav files I may be able to resurrect so nice old recordings.
 
Groovy!