Have a read through Canadian Couch Potato. He does some good articles on when to hold US$ ETFs (when you can do the forex cheaply, and in an RRSP or unregistered), when not (smaller contributions, in a TFSA, etc).
If large $ amounts, Norbert's Gambit is your friend (TD won't tell you about it); basically buy something 'interlisted' and journal it from the TSX to the US side. Assuming they allow you to hold US$.
TD eSeries do NOT have a high MER, generally speaking; they are very good. They just look high compared with some of the US Vanguard stuff - but compared to pretty much anything else (ie any other mutual fund), they are cheap. You will save some money if you go down the ETF route, but *action* is the most important thing. Start up your contributions and keep them up.
Some ETFs to look into:
ZEA.TO for a *non-US wrapper* non-US developed market fund - it holds the shares directly, saving one lump of withholding.
IMHO if you have a brokerage account don't let them manage anything, charge anything, do anything. Just buy ETFs as and when. Ideally in (at least) $1k chunks, which is effectively a 1% front load fee. $20k? Great.