Any suggestions for good luxury/semi-luxury small tours in India, probably Northern India.

There are nth possibilities of such a tour in Northern India. It all depends when you wish to visit India & what are your specific interests. An itinerary can be tailored to fit you & not the other way round, much like shooting in the Bunker Trap where the gun must fit you!!
I have given a vivid description of what you can expect in Himachal, in another post, a minute abreast. You have other choices to make like Rishikesh where you can see Hindu mysticism at close quarters. Rajasthan is full of those lovely fort-palaces where every stone has a story to tell, as much as normal touristic places.
Some bold spirits are as yet fighting for the Indian wild-life & tigers. We have a couple of great tiger reserves in north India. In one such destination you can stay inside the park & listen to the animal calls at night, adding pleasure to an already amazing setting.
The temples, some of them done in stone, what it would be difficult to achieve on canvass & not necessarily all religious images but also rooted in those ancient contemporaneous times, could be a part of your plan.
Happy travels!

I am looking for the same type of tour. What do you think of A & K and Tauck. Have you checked out any other groups?

In times of economic meltdown, gentlemen, better to look farther afield than the brand names! You have so many recommendations on this very forum...great personalized service, customized tours & competitive prices!!
Very best for your plans!

Bravo for the above, Mr Singh! Why not support an excellent "home grown" service, rather than a huge company with branches in every city in the world?
If it were not possible to get a great Indian company tour, it might be different, but there are wonderful "local" companies. Their owners and employees know particular regions well...because they live there!

Although Mr Singh is far too modest to mention his own company, my husband and I traveled with Legends and Palaces last year and can highly recommend him. And no, I'm not getting paid to say this

I must agree with MsSommelier.
My wife and I travelled with VP in 2006 and he is the BEST. You will not only see India with VP - you will feel it.

Have a great trip.

The best "small" tours are the ones for you alone. Any of the India travel agencies can set one up for you. Do your research - decide where you want to go, then ask several of the well-recommended companies mentioned here on Fodors to give you a price.