I just had to Comment on the original question asked and then some.
How do Line6 Amps compare to the POD ...actually they compare pretty well the POD 2.0 is closest to Flextone II Amps and PODXT closest to Vetta, DUO Verbs and New
Flextone III.
Better off Buying POD and separate Amp depends on what you are trying to accomplish. For direct recoding the POD is great and if you are trying to get the same tones live as you record direct, then you may want to consider a Line 6 amp for Both. But neither option is a bad choice depending on the funds you have available.
For Myself I own and LOVE all my Line 6 Stuff and use it daily without problem so far. I have a POD 2.0, a Bass POD, A Flextone II HD, a Line 6 4x12 slant cabinet (412S) and
a floorboard. Before I bought the FlexII HD and Cab I played several Marshalls and Mesa Dual Rectifier Head, Flextone IIXL 2x12 and a few others. In
the end the Marshall, The Boogie and the Flextone II HD and 412S Cab were the final ones in contention and I choose the FlexII HD and Cab, Why? For me the flexibility and tonal combinations it offered out weighed everything else for me. I loved the Boogie and the Marshall but neither offered IMHO the flexibility that FLexII HD did. When I played the FlexII HD with the 4x12 cab it sounded exactly like what I was hearing coming into my headphones from the POD, and it just blew me away and still does to this day. I also want to be able to reproduce the same tones live that I was multitracking in my recording setup.
I will be honest though I played the flextone II XL and considered it for half the price and liked the it, but IMHO
the FLextone II HD and Cab just sounded so much better to my ears and much closer to the way the Pod with Phones or direct into my board sounded. To me it just has a lot more balls.
I want to be clear this is not a knock at the Marshall or Mesa Amps they are great AMPS as well and probably better for clean tones to a degree, but neither gave me the tone flexibility Line 6 did.
The Vetta HD was also just out when I bought by Flex II HD and I choose the Flex II HD over that just because I knew the way the POD sounded and loved it, and at the time was able to reproduce those same tones with the FlexII HD live much easier the with the Vetta, I am sure familiarity of how to dial in tones helped. The Vetta and POd XT do have some very cool features as well over and above the POD and Flex II amps but not necessarily the same tones.
And finally if you will to spend the timeexperimenting with the Line 6 amps (I personally don't care for many pre-sets) and aren't afraid to turn some knobs you can get incredible guitar tones and with my setup also at real loud volumes. I have had a plenty of people who have heard me play thru my AMP who are just blown away by the tones and number of great sounding AMP tones I can create with the thing. I for one feel Line 6 makes a great product that sounds great and is extremely versatile, especially if you are using them to record and have the need for lots of different guitar tones.