for home practice i wouldn't suggest getting an amp unless u're really on a budget. if u can, try get a pair of stereo monitors. that'll really give u the true sound of your keyboard. plugging in mono just don't do keyboards justice, IMO. the best value for money solution - headphones.
the altec lansing will blow out on your keyboard. it won't be able to handle the full range of frequencies as it's not a full range speaker. if u try, your keyboard sound will be terrible too. if you have a hi-fi, you'll be better off plugging in there.
you could try looking around for a cheap and lightweight 61-key controller. such as radium61. you could get back to me on this later, might be letting mine go if you're interested.
