Ok, so I have been having a ton of trouble recording soft synths/vsts ect as my latency is out of this world.  Under my device settings it shows me to have a very low latency, but once I try to play something its a VERY noticeable difference between key press and sound delivery.  
 
Here is a quick run down of my gear and how its setup:

1. Custom Built PC running Windows 8.1+ 64 Bit (Core i7, plenty fast harddrives, 8GB RAM) - was built a few years ago but should still be plenty fine, and I will be upgrading to 16GB RAM when I can, but that shouldn't be the issue.
2. Mackie Onyx 1640 (original) - this is my audio interface, and is done through the Firewire output.
3. Sonar X3 Producer
4. Novation SLMKII controller
5. MOTU Micro Lite Midi interface

 
I route input/output through the Onyx mixer.  Audio playback & recording are fine, but try to use MIDI and all hell breaks loose.  Its almost impossible to record vsts on some songs, and its killing my creative flow :|  
 
I have tried all driver combinations, including ASIO4ALL ect.  I have to put my ASIO buffer all the way down to 32 in order to record in "real time" with vst/midi, and at that low of a setting, the audio playback starts to fart and crackle so thats a no go either.  
 
There is also a noticeable lag/latency when recording audio with INPUT ECHO turned ON when you want to hear effects used while singing for instance.
 
Anybody have any advise here?  I'm not sure if I need to replace my original Onyx mixer with something better, or if I'm missing something simple here.  
 
Thanks in advance for any guidance here, as I'm in the middle of an important project and stressing out big time.

While I have no experience with the Mackie Onyx 1640, the following thread seems to indicate the latency for this unit is high :
 
(post #9 by Jim Roseberry)
http://forum.cakewalk.com/Mackie-Onyx-1640-with-fw-Latency-m1060626.aspx#1061437
 
You did mentioned recording audio is fine - is it due to direct monitoring, that you did not really listen to the ECHO ON audio ?
 
And later you mentioned with the ECHO turned on, the audio latency is noticeable ? (similar to midi latency ?)

I suggest running with Sample Rate of 48 k, ASIO Buffer Size of 128, and record bit-depth of 24-bits.  Try to get your Total Roundtrip Latency down around 10 milliseconds or just a little less.
 
Also, I would UNINSTALL ASIO4ALL completely, as you have an audio interface with ASIO drivers.
 
lastly, as a test, please set the settings to what I list above, then for this project, hit the 'E' key on your computer keyboard and see if the latency goes away.
 
IF hitting 'E' (which bypasses all effects) make the latency go away, then that means that at least one of your effects plugins is NOT meant for use during recording, but is instead a high-latency inducing effect meant for mixing/mastering.
 
Please perform the above tests and post back with the results.
 
Bob Bone
 

Thanks for the replies!  I will try some of that.  Right now my settings are 48K, 24bit, but I've had to get my buffer size down to 32 to make it useable.  

However, I will try to hit "E" and disable all my plugins, and it may just be as simple as you said, where there's just a plugin not meant for use during recording ect.
 
Tomixornot:  I don't use input echo except when doing vocals, and the lag I get from that is very similar to the lag I get while doing midi.  I never have any input echo's on when doing midi though. 
 
I will also try to remove ASIO4ALL since it seems not to serve any purpose.

Is your controller hooked up via USB?

Well....I guess its been solved.....I should know better.
 
Robert_E_Bone, I took your advise and disabled all plugins ("E") and midi records just fine now.  Guess I will just get in the habit of doing this while recording VST's.  Thanks again everybody!
 
Sharke: My controller is through the MOTU Micro Lite, which is USB yes.

@dtboos - while you can, I suppose, use the 'E' bypass to allow you to continue to track, I was suggesting you try it only as a 'test' - to see if the problems were from one or more of the loaded effects.
 
You might now consider temporarily swapping out the problem plugins - just until you are completely done with tracking, and then when you move to the mixing phase you could put those effects back in (and adjust your ASIO Buffer Size way up to allow them to do their thing properly).
 
The kinds of effects that are really meant for mixing/mastering include those that use something called 'look-ahead' processing, or otherwise consume lots of CPU.  Examples of these kinds of plugins would be: Boost 11, Perfect Space, LP-64 EQ, etc.
 
So, swap out if you want to hear effects while tracking, or if nearly done and are OK with it - perhaps simply bypassing would work for you.
 
Next project - don't load plugins that cause latency problems, until you are completely through with the recording process, then crank up the ASIO Buffer Size and load them in for mixing/mastering.
 
But, glad you now have an idea of why you were having the issues.
 
Bob Bone
 

Robert,
 
That sounds good.  I'll be figuring out which one(s) are the culprits and keeping them out until the mixing/mastering process.  Appreciate all the help, I was panicking for awhile there.

I usually get legged up by my FabFilter plugins; they're great but will cause latency (on MIDI also).

I'm just glad it's all sorted out for you.
 
This issue is QUITE common, but can gray you up faster than being President, and almost as fast as being married.  :)
 
Bob Bone