Need advise on amp choice

I have done intensive reading trying to solve my dilemma but still no success booked...
I have got a pair of SF Strads, an ARC LS26 and I wonder what would you do if faced with the following choices:
- used ARC Ref110, 3 years old with 1643 tube hours for the half of the original price
- used ARC DS450, 2 years old for the half of the original price
- new ARC VS115 for the price of the above mentioned Ref110
I am a little worried about the noise made by the 2 cooling fans in the Ref110 since I love the silence between the tracks; it doesn't have the latest KT120 tubes and, according to ARC site, I will have to invest soon in new tubes anyway...
I have had a new dsi200 for 5 months now but it wasn't by far a match for the speakers, luckily I was able to sell it.
My dealer insists on buying the VS115 but it's in the run from 2008 and, following the company policy, it should be discontinued sometime next year - not a much of a reason but still...

I have not heard the DS 450. I much prefer the Ref 110 over the VS 115. And a Ref 110 for $5000 is a real nice deal. I have owned and listened to a lot of Audio Research amps since the mid 1980s. I currently own a Ref 110 and am very happy with it. I don't hear the fans from my listening position. I would call ARC but if they are a problem I believe they can be unplugged. I don't think the fans are really necessary if the amp has good ventilation.
Thanks Lostbears, you are probably right changing the tubes scares me since I am not used to tubes at all; for the convienince I would prefer the DS450 - lots of power but I didn't have the chance to listen to it...
"Advice", not "advise". Your 3rd grade teacher is crying.
"Your 3rd grade teacher is crying."

So is yours, for failing to place the comma following "advice" and the period following "advise" within the quotation marks.
You dropped out in the 3rd grade?
You are hilarious,I nearly spit my Macallan single malt out reading this, every time I see this misspelled,(far too often) I cringe!!!
On a more productive note, I would definitely keep the REF110 and put some KT120's in. I can tell you from personal experience, they are great tubes.
what would you do if faced with the (...) choices
I prefer the sound of the Ref110 to the vs115. I've only listened to the 450 once -- so no opinion.

OTOH, experience with the other amps is based them driving small SF (the same pair, in fact!).

BUT when I had the Strads at home I only *just* drove them correctly with 250W class A SS per channel.
(Outstanding speakers!)

And the 450 offers the advantage of 450W of power / channel...

So, I would go for the 450. If I didn't the sound I'd look around to improve -- but at least I'd know it was driving my speakers correctly, if not to my liking!
Spelling police are in force!
Sorry for the spelling and many thanks for all you reactions; I have ordered the second hand ds450, it should arrive next Wednesday...
I should probably add a signature containing "the guy from Holland" to avoid/reduce spellings remarks - nevertheless useful
Congratulations on your ds450,I hope it sounds great!