Pre-amp, integrated, new power amp...I'm confused

OK, after posting many threads and reading tons of old threads and reviews...I"m stumped. I have a NAD C370 integrated powering SOnus Faber COncerto's (Home Version), a Cambridge audio Azur 640C CD player going through a musical fidelity tube buffer(my one and only audio source), Cardas Cross IC's and speaker cables. A REL Stadium III handles the bottom end. I love my system, excepy for a little graininess in the top end. I would like to smooth out the sound and make it more liquid and natural. How do I best accomplish this? DO I invest in a whole new integrated? DO i Drive the power amp section of my NAD with a tube pre-amp? DO I invest in a better Source (New DAC or whole new player). I like the sound smoothe and natural...maybe a little warm (Which is why I chose SOnus speakers. I would like to spend no more than $1000. I saw a BAT VK-3i tube preamp available. Am I on the right track with that? Help!
Depends on how much you want to upgrade. If you have 1000 to spend, is that it, or will you have more in a couple months you can set aside? If that is the case, start with a pre amp or power amp now, knowing you will upgrade the other shortly.

If the 1000 is all you'll have for some time to devote to audio, refer back to your integrated amplifier thread you started and take some recommendations from there.
Sell your integrated and buy a primaluna integrated. I think it has the sound you are describing. Well built too.
It's unclear whether your source, NAD amplifier or both are the cause of the graininess. I suspect it's a bit of both.

I definitely wouldn't go the route of a new preamp. The Cambridge 640C is fairly well regarded. I like the recommendation of the Prologue 2 integrated amp. Perhaps a good plan would be to purchase a used Prologue 2, try it in your system and see if the change results in some improvement. If not, then sell the Prologue 2 and investigate a new CD player, but I have a hunch the Prologue 2 will be an improvement.
OK, i have decied to go the route of a new tube based preamp. That seems to make the most sense to me. I think the NAD amp section is good enough for now. I did some calculations and when I bought the NAD new, it was only $80 more than a matching NAD amp only. That probably means NAD only spent around $100 dollars on the line stage in the integrated. I don't need A phono section, because I am not going to be getting into vinyl anytime soon. I have my choices down to 3 preamps:

BAT vk3i
Rogue Magnum 99
Jolida Music Envoy preamp

Which do you people think would be a better performer?

Thanks in advance!
With the preamp, you are adding an additional element into a system that already has grain according to you. It's not possible to eliminate grain by adding more electronics. You can eliminate grain by substituting electronics that have better power supplies than the components you presently own. In fact, since a preamp will likely be more resolving than the preamp section on your NAD, adding a preamp may highlight problems with grain from your Cambridge CD player and make your problem worse.

IMO, you're making a mistake with the preamp, but if you're going to buy one, then buy a used one and choose one that has strong re-sale value, because these are all starter preamps, and you're not going to have any of them long.

There's no clear path to success in this hobby, and part of the fun is the discovery. You're in for a really good time! :)
If the MF tube buffer didn't give you the sound you're after, I doubt adding another tube component will do it either. Also, before adding a tube preamp to your NAD integrated you need to know the input impedance of the NAD amp section.

Probably a better route, as others have mentioned, is to replace the NAD completely. I have owned and enjoyed the Jolida 1501A. Rogue makes an entry level integrated that is probably worth considering.
I really second Tvad, adding a pre, albeit tube, will not eliminate the grain in your system. I think taking a closer look at the source would yield better results in the end. I see you have MF tube buffer; wonder why you got it in the first place-were you unhappy with the sound straight out of the Cambridge?
To add to your confusion, I would suggest a simple solution.

*Park the MF buffer.
*Purchase a nice used integrated for ~800 or less -- many here at Agon (vintage Acuphase, Nuforce, Krell, A-Analogue, Opera, Simaudio, Pathos -- even a diy gainclone...).
*Connect the cdp directly to the integrated using single core wire (solid conductors - not stranded) -- take yr pick on that there's many around, and they're generally inexpensive. You can even get gold-plated silver wire

Take Tvad's advice: you don't NEED separate preamplification, but you may need a little bit of power.

OR, coming to think of it, hook the cdp directly to yr amp now. Check out the differences if any. COnnect a tuner (borrow one). Check the sound.
And come back to us.
The grain is from the CD player, that player is good, but you are hearing its limitations. Get an outboard DAC for cheap like a monarchy audio DAC and see how it goes. They are cheap, you can experiment and then sell for what you paid for it. Great opportunity to start testing digital stuff out.
My suggestion also echoes the suggestion to eliminate the tube buffer. That step goes without saying, but it's good that it was specified.

The idea if a DAC is another possibility, although I tend to think it might not be as satisfactory as completely upgrading the source or amplification. Adding a DAC presupposes the transport section of the Cambridge CD player is worth keeping. It may or it may not. I don't know the answer to this.

The preamps least the BAT...sell for more than $1000 used. For that kind of money you can buy either an excellent used integrated tube amp (or solid state amp), or a used Rega Apollo CD player. Either will be a substantial improvement.
Thanks! I see all of your points, and they are all valid. I think I'll hold off on the Preamp. I'll do some experimenting, and take a hard look at my source. SInce it is my only source I should treat it well. A new integrated is not out of the question either. I thank you all for keping me from making a costly error (costly for me anyway) Thanks again!
Just want to add another possibility..I would't add a preamp to this mix...I would look into a good tube integrated, ie primaluna prologue 2 or TAD 60 which i have at the present time...This is an extremely well made single input integrated or can be used as power amp with a separate preamp....I was lucky enough to locate a rarely available TAD 150 preamp...and the combination is truly wonderful...You can read lots of review on the forums about both of these pieces