Currently, the G70 can only link .txt files to SMFs, but the new E80 can link to styles as well (also link .bmp files), and we are all hoping that Roland will update the G70 OS to allow this feature - they have been very good at adding new features and fixing bugs since the G70 first came out......
The G70 has a USB connector (slave mode only) so you can't hook your hard drive directly to the G70, but you can transfer your files to a computer and then USB them to the G70's internal flash HD, or an external card (or, if your computer has a card reader, write them to the card and then put the card in the G70). So....... plenty of easy ways to git 'er done!
I think the G70 has an upper limit of 4GB for card memory.... MORE than enough for MIDI and .TXT files....
BTW, dnj DOES tend to get a bit partisan about whatever he's currently using, and I really counsel you to try before you buy (and more than ten minutes!). As everyone's been trying to point out, lately (I guess Lebanon is showing us the result of lack of conciliation!), ALL of the top of the line arrangers are great (I've never - other than jokingly - said the Tyros2 or PA1X are bad arrangers!), it's more a case of what works best for YOU.........
There are many things to like about the Tyros2 - OOTB the styles are very good, some of the SA voices are jaw-dropping, a sampler, if you need one...... but for me it doesn't work. I prefer a 'live-er' sound, and have to have 76 keys for SMF play, I love the FC-7 for foot control, many other reasons. But for you, it might be different.
These arrangers are SO expensive, do yourself a favor and really give it some time. There are far too many of the 'rolandhaters' (we know who they are!) that actually BOUGHT one, and then decided they hated it......... how dumb is THAT! ;-) Part of their dislike must come from kicking themselves in the rear about a bad decision and transference to others that make the same decision they regret!
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An arranger is just a tool. What matters is what you build with it..!