This would be my recommendation based no my own set up. I have the new sigma 35 f1.4 lens and 85 f1.4 lens. They are all I really need in terms of focal lengths. Their low apertures give you alot more control over depth of field and allow you to use them in low light. they are also sharp even wide open. However, for travel, I would rent a very nice zoom like the 24-70 f2.8 II. See, I dont travel often, maybe twice a year at most, so buying a zoom is worthless for me because every time I have owned a zoom in the past, I would always find myself hardly using it in favor of my primes. I used to have the 24-70 f2.8 I. Its soft wide open, heavy, and suffers from barrel distortion at wide angles. The difference between 2.8 and 1.4 is like night and day, especially when it comes to low light and subject separation. If you dont see yourself traveling often, I would stick with primes to really take advantage of that FF sensor and just rent a great zoom (insured of course) for when you do travel. If you travel often, then I would agree with everyone else here pick up a zoom. Primes are a tad too difficult to deal with when it comes to traveling as moments can come and go quickly and a zoom will be better at catching them vs a prime.