I'm not sure if this is the proper forum, but here goes.
 
With SONAR Platinum and some Waves plugs I think I may be able to improve my input quality by introducing a nicer preamp.  I've been looking at a ssl alpha vhd, does anyone have experience with this preamp vs. the alternatives?

I almost bought one years ago from a studio friend.  Good kit.  I can't remember much about it except it sounded a lot like his SSL G, which is a good thing ;-)
 
A good preamp can make a difference once you reach a certain level of hardware and craft, and SSL ain't no slouch.  The great thing about step-up hardware as opposed to built-in pres is running them hard.  Sound that would break-up an interface pre gets captured when the singer decides to belt out during a ballad - and that works and you aren't left with a crisped mess.  The SSL pre has the saturation button, I think, which makes it sound like an older pre, so you do have flexibility in the sound.  There are lots of other reasons.  However, a good pre ain't the answer to everything.  In general, the closer to the source (mic, for example), the greater the influence of the hardware.  A good pre will make your 57 sound better, but not like a condenser.  However, the same sub $100 MXL ribbon that I use on electric guitar sounded just as incredible on a trombone solo I recorded this weekend.  It was going through a RND portico II, a top-end pre.  So there are no rules, only guidelines.
 
On the lower end, WARM audio and the Focusrite ISA One are both fine, professional preamps you can find for less than $500, while the RNP gets you two transformerless pres for the same cash.
 
 

Thanks for sharing your thoughts. 
 
I have some decent mics, oddly all Shure - SM7, KSM-44, SM-81(2), and think the preamps are the weak link in my chain right now.  I had been considering the ISA, but this SSL came up for sale locally at a good price.  I like that it has the saturation and can use the hi z input.  I thought about the RNP, but the form factor seems a bit awkward (which I suppose is part of the bargain).

If you can get a great price on the SSL that sounds like the deal.  If you trade it out later you probably won't lose money, tho it probably is a keeper.  One point about the ISA is it can use the transformer either inline with the mic or the DI, and you can use the DI as a second input as well as the mic pre.  A flexible little unit.
 
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