Help need an amp for Infinity Sigmas

When you say to weak I asume you mean the mid and high tweeter section.
The IRS Sigma is slightly different hence it was developed after Arnie left Infinity.As far as I know Arnie does all development with tube amps so I would suggest you try first a tube preamp and one of your power amps and see how it sounds.

I have a pair of Ren 90's which are very similar in design to your speakers. I drive them with a Threshold s 500 II to very satisfying results. I did though fry one of the Watkins woofers New Years Eve but I attribute this more to using poor MP3's as some of the source material. The Threshold drove the speakers to almost live levels in my 22'x33' x 19' living room. No damage to the Emits or Emims thankfully.

If you are not in a hurry to get the amp, I would urge you to wait a couple of months for the PS Audio Power Frame (www.psaudio.com). Paul, head of PS Audio used to work with Arnie of Infinity and Genesis fame and worked on the Stealth amp that drove one of the larger Genesis models' bass section.

have you considered Classe'? A single or pair (to vertically biamp) of the CA-300, -400, -301, or -401 would be worth trying for better sound and less money than the ML's. dealer I used to frequent in Texas had everything imaginable (wilson, levinson, krell, wadia, you name it)...best sound he ever put out was the Infinity Epsilons (model up from Sigmas) run by a pair of CA400s.

Paul,
thanks to your response. Tube amps is a new topic for me,
but when the time comes I'll look in to it.

336 would be a good choice, very detailed and open-sounding amp. I have a classic pair of Infinity RS1b that requires bi-amping, and I use an older Levinson ML3 on the woofers, and a 333 on the mids/tweets. This has been a more than satisfactory combo.

If you move to Genesis, most of their speakers come with amplification for the woofers, and you'll need to look to tube power for the best sound from the mids/tweets. ARC VT150SE's come to mind, as would the Expensive, but excellent McIntosh MC2000. A friend has Genesis 200's, and drives the mid/tweet panels with the Mc 2000, his system sounds great!

Hope this helps!

Paul