Mcintosh MC240 + Audio Research SP-8?

What aspect of your system's present sound are your trying to 'improve'. And, for those of us not intimately familar with your speakers, what is their nominal impedence, minimum impedence, and what is their efficiency spec? What in your budget for this 'improvement'?

Specifications from Stereophile review,

http://www.stereophile.com/content/dynaudio-evidence-temptation-loudspeaker-specifications

And Captain Kirk said, “Scotty, we need more power!”
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Newbee makes a very good point. If the choice was mine to make, I would definitely go with a new preamp. But thats just me.

That MC240 is from the 1960s and is probably worth more than you paid for it. Original retail was $288.00! They sell for over $2k now, which is fine for collectors but is not for someone looking for best sound.
The SP-8 is probably a better bet sonically, revered for its sound quality more than its collectability.
If you've got the model right, those Dynaudio speakers retailed for $30k and deserve better electronics. Go find a Dynaudio dealer near you to get a better idea of what you should do. IMHO, do not buy replacement electronics without listening to them first!