snikr
Hello & Welcome to the Forum.

In answer to your question, Yes, but...
with the O-27 curves you will want to stay with  x-4-x or x-6-x with blind driver, wheel configuration.
O-27 is a bit tight for flanged center drivers , not saying it can't be done, but wheel and track wear as well as binding can occur.  Deciding on which locomotive, pre war, post war, MPC era and modern give you quite a choice, but will possibly be best if you choose a locomotive that operates conventionally, that way you won't have to purchase a new operating system transformer if you have an old style transformer.

Happy Rails.
Dave

Well, purchasing another set is an option. In the classified sub forum, members have trains listed for sale. Many of the posts may be old, but it is quite possible their trains are still for sale.
Yes, I do have trains listed but they probably aren't what you want to expand your empire.
If there are any train shows in your area, check them out. You never know what you will find.
Local hobby shops & craigs list are options for finding trains.
What ever you acquire, make sure it is compatable with what you already have.

Happy Rails!
Dave

A CHILD AT HEART, STILL PLAYS WITH TRAINS!