There are a myriad of different ratings and listings for low voltage transformers. Far too many to get into all the details here. Bottom line, if you want to be code compliant, you must only install transformers and components that are approved for their application. In this case, if the transformers are going to be installed inside the home, they must be ULc, cETL, CSA, cTUV, or cMETus approved for indoor and outdoor applications. (few are). Of course you must also ensure that the transformers being used to power low voltage landscape lighting systems are also appropriated listed for that application. It is not appropriate to use interior/remote low voltage transformers to power landscape lighting systems. If the transformers are being installed inside the home there are other issues regarding the type of wire used inside, how that wire transits to the exterior (conduit is required) etc. It can be done properly, but does require a bit of knowledge and some extra attention to codes etc. Ultimately, as the homeowner, PLSwest can pretty much do as he chooses. However, if the installation is done incorrectly and a problem develops his insurance may not cover the DIYer / out of compliance installation. Also it can be an issue come re-sale time. There are a lot of advantages to hiring a local, experienced, licensed/approved professional to work on such things. Well worth the extra money.