Starting out O-Gauge

I'm pretty sure you will need to tell everyone what type and brand of locomotive model you are thinking of purchasing.

Most of the newer engines will work with Lionel or MTH transformers. The only exception would be the CW-80 and an MTH PS-2 engine.

Like Hot Water mentioned; it would help if you mentioned what brand of engine and transformer you want to use with it. Examples would be; a GP-30 made by Lionel, or an SD-45 made by Williams, and a Lionel ZW transformer, or an MTH Z-1000 transformer.

Also do you want to run with a command control system? There are at least three on the O gauge 3 rail market, for Lionel there is Legacy or TMCC, and for MTH there is DCS.

Lee Fritz

Depends on the Loco and company.

Lionel, MTH or Bachmann

Bakdrft,

    This all depends on how big your layout is going to be and how many engines and lighted/operating rolling sock you are planning to have along with how much space you actually have to build your layouts in.  If you are planning a fair size layout I suggest you skip the medium size transformers and purchase either a Z4K or a ZW-L.  You can also pick up an old ZW or 2 and add external breakers if you plan on running DCS and Legacy. Lots of different ways to power your modern layout, Guns likes the PH180 and the bricks, you might want to consider this also.  Now if you are only going to upgrade your RTR set to a medium size layout, and go no further with your expansion, I recommend the MTH Z-1000 transformer it is a serious cost effective modern power supply.  I always tell everyone to over power their layouts to allow for expansion.  You simply need to decide on how much power you are going to need for the space requirements you have, and how many engines/operating rolling stock you want to run. We have a multi-level layout in our home at Christmas time, and our power station consists of 2 Z4K's, 3 old ZW's, and 2 old KW's, for powering my multi-Level DCS/Legacy layouts each Christmas.  The more Engines,track, accessories, and lighted rolling stock you have the more power you need to operate your layout.

PCRR/Dave

Command, and layout size are the big questions and answers here.

So lets start with conventional.

Nothing smaller than a 90w 1033 or CW-80.

"Overpower your layout to allow for expansion"

Buy big watt units if its an option, or be ready to accept more limits

 On any layout, an 80-90w unit barely "gets it".

A great match for my size actually, 4.5x9. Most locos can be run at or near full throttle with not too big a load, but can be loaded to "circle like a wagon train" too.

 But double heading a couple of big amp units? Running a bunch of accessories too?

Lighted passenger cars? Either more of them, or bigger ones will be better.

 New whistles often don't work as well on PW transformers unless "diode updated".

  PW air whistles don't work as well on new ones. They like the 5v boost on older transformers.

  An old transformer, and new controls allow more versatility. 

Conventional alone? Only new transformers have a bell button! Many new trains have bells! Control systems can do it, but otherwise you might want a bell button too. 

 Pure sine vs chopped, and a best guess as to how that might affect your future choices should be looked at too. I think full sine/traditional power updated, is compatible with more systems?

My view on command...

MTH has the best versatility, some TMCC commands "built in".

TMCC (cab1) - Popularity leader, some basic legacy control

Legacy(cab2)-  All the latest Lionel bells and whistles".

As you can tell by now, everyone does have the desire to offer advice. Hot Water is correct in asking what make and type of engine you're wanting to operate. Your answer will unlock the door to a massive library of knowledge. Yes, such a place does exist. Right here on the forum. I did avoid all the "mumbo-jumbo" for the sake of keeping it simple. BTW I will never ever hold a grudge.