Roland's figures are confusing, to say the least....!

To compare (in simple terms) the G70 and E80 - the E80 has more ROM memory, but uses it on fewer sounds (but more drumkits). Many of the original Sound Canvas sounds are now gone from the E80, but still in the G70 (something you may need for easier compatibility with older Roland styles and SMFs, though the Makeup Tools make conversion pretty painless). The E80 has the same piano as the RD-600SX, the G70's is from the FantomX (both are superb).

To compare the E80 with the E50.... although the Mbit/Byte confusion is all marketing hype (MByte, or MB should be the common comparison standard), at least comparisons can be made using Roland's own info.

The E80 has 128 note polyphony, the E50/60 has 64, so an obvious difference there (although I never noticed much stealing on my old 64-voice G1000).

The E80 has 1024 Mbits and the E50/60 has 512 Mbits, so half the waveform data.... The Hammond (HB in Roland-speak) section voices are not counted towards waveforms. So nearly as many voices (Tones) with half the data. This will account for some of the loss in fidelity as Roland may compress the waveform data harder in the E60 to squeeze more sounds in.

Also, from extensive listening to G1000 and G600 side by side in the past, I have the distinct impression that Roland use less expensive D/A converters in their mid and low-end lines. I always heard a bit of 'brittleness' to the sound of a G600 patch, even when playing ostensibly the EXACT same patch as it's G1000 cousin. This may be due to the sample compression alone, but I always felt that it was probably a combination of the two....

Obviously, you are not going to get close to the sound of an E80 in an arranger that costs over $2000 LESS, but specs aside, the mid-line Roland arrangers should fit many people's needs, especially in the area of ease-of-use. Roland's style and SMF 'tweaking' utilities are still some of the best and easiest to use in the industry, and the overall feel and ease of use of the OS may persuade many away from more complex to use arrangers, without giving up good styles and sounds.