I'm at 4.5GHz with similar scenery, the NGX and so forth as you. The T7 ever so slightly lowers performance compared to the NGX on my system, mostly in bad weather (ASN/REX) over say Aerosft Manhattan X. I would say you're good to go. Enjoy, it's a fantastic aircraft.
With default scenery you would probably maintain the same performance as you are used to for the most part. Adding in detailed scenery, airports, textures and weather you would probably need to lower some sliders to maintain the performance you are used to. That said, what makes up your present FSX add-ons and settings? With these details a more accurate analysis may be obtainable.