best preamp under 4000 to match 4b sst

I wouldn't buy either an Isabella or Dodd preamp new. I'd wait and buy a used version.

When you resell, you'll lose half the value if you bought new.

Given the option, I'd buy one of the used Dodd preamps. Try it, and live with it for a while. If you decide to try something else, then you'll recoup more of your investment.

You could also still use a Lamm LL2 Deluxe with the 4B SST. Those have held steady at around $2500 for the last four years.

500 isn't that much, given the full waranty, local dealer support and trade in option towards future upgrades or purchase.
Both brands are exceptional and pleasure to deal with.
Whatever you end up choosing, it won't disappoint.
I guess the decision will have to come down to small differences between these two and customer support.
I own(d) both of them and can't say anything bad about'em .....even if I tried.

Can you ask your dealer for audition or take it home for a test drive?
It would make sense before pulling out the plastic.
It would let you sleep better knowing that you've made the right decision.

Cheers
Mariusz

Tvat, I haven't seen Dodd or RWA Isabella at 50% off.
Also , (I don't know about Dodd) RWA has generous trade-in program.
Vinnie might even give you full list price for your older RWA component towards the upgrade to one of his more expensive offerings.
I am certainly pleased. YMMV
One of the best customer support that I've ever encounter.
Just to give you an exemple: when I questioned Isabella's performence and doubt it being better then my own Dodd, he showed up in my house with Isabella in his hand. And no, I am not the next door neighbor. It is at least few hours drive......not many would go to such a lenght to please the customer.
I doubt that you are going to get the same service from Joe X buying used.
It is your call.
Again , nothing wrong buying used but it isn't always the case.

Mrstark, I can see I need to be quite specific here.

One can lose anywhere from 20% to 60% when re-selling a piece of
equipment originally purchased new, give or take a few percentage points
higher or lower adjusting for market supply and demand.

There is a Dodd preamp for sale now listed at $1795. Its retail price is listed
at $3300. Therefore, the asking price is 54% of the original retail price. The
preamp has not sold at its asking price for 11 days, so one can assume the
actual sale price will be less than $1795. I'll venture a guess that it will sell
very close to 50% of the original $3300 retail price, give or take a few
percentage points higher or lower.

The Isabella is a relatively new product, so there have been few, if any, for
sale on the used market. However, looking at the listings for Red Wine
products shows asking prices ranging from 60% - 64% of retail. So, it may be
true that an Isabella would sell for more than 50% of retail.

Nevertheless, 40% is a significant savings.

I have head nothing but good things about Vinnie Rossi, and I imagine he
would offer excellent service for any of his products whether they were
purchased new or used.

Excellent service has been provided to me on used components from the
following companies: Lamm Industries, VAC, Modwright, and Exemplar Audio.
Frankly, I have never had a bad experience with any manufacturer regarding
service, information, or support on used components.

However, if the OP feels more comfortable buying new, then that's absolutely
the way to go for him. I agree with your suggestion of a home trial.

>>Mrstark, I can see I need to be quite specific here.<<
So do I.

Your experience on used market simply can not be matched. (ALNBM)

>>Frankly, I have never had a bad experience with any manufacturer regarding
service, information, or support on used components.<<

It is not always the case. One of the most reputable speaker manufacturers would not even answer my question and openly stated "no support to second hand owners". YMMV

>> I'll venture a guess that it will sell
very close to 50% of the original $3300 retail price<<
(please check the Dodd website not the listed prices on AgoN)

Ones again, the retail on Dodd battery preamp is $2699 NEW (directly from Dodd Audio). Please do not tell me how much it was a year ago as the author is shopping for preamp right now.

Now, about Maverick_spd's case.
We know that he lives in Canada.
We know that RWA has a dealer there and Dodd Audio doesn't.
We know about shipping costs, customs & taxes, exchange rates and repair costs if the product isn't under warranty or if warranty isn't transferable.

Do you still believe that used Dodd is a better choice????
I love that preamp but it just seems like Maverick might be better of with new RWA preamp.

Your philosophy is valid but like I said earlier.........."it isn't always the case".

Mariusz