I don't download so can't offer you a 'Best Buy' so to speak, but as far as using dial up is concerned, yes you can do it. It will obviously be slower and you will be on line longer so the issue must be, are you on a Pay As You Go connection or a monthly contract?
If PAYG you will need to compare the cost of actually buying the CD you want against the cost of your telephone call. If it's contract, do you have any sort of limit on the amount of data you can download?
Finally, how reliable is your connection? If it's forever breaking down you will need to consider some sort of download manager that will pick up the connection again from where it left of.
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Do you know that we're all in line for succession to the throne? Really?
Well, if forty-eight million, two hundred thousand, seven hundred and one people died I'd be Queen.