Theres deffinitly world class fighters that Chris could still outfox but anyone with a high workrate would be difficult for him.

Light heavy weight would be his ideal weight as his normal day to day weight doesnt exceed the Cruiser limit (especialy since they upped the limit).
Carl Thompson is a well regarded puncher and Chris had no problems taking some clean shots off him but its just the basic body strength that they have over Chris.

I think an ideal opponent for Chris would be Tarver, I think hes a little overrated because his biggest wins were over faded old fighters and he also has only Two different names on his resume in 3 years. tarver faded badly against Jones who was scared to do anything and Chris always had good stamina