Some factors to consider- how much $$ do you want to spend? And, are you using or ever considering using the JTV with an HD500?
I already have the HD500 floor POD, looking at add a JTV59 soon..
Beyond that, I can' speak from experience yet, but will be soon -as the DT25 I just ordered is arriving tomorrow! I am on a little tight budget, so ended up ordering the DT25 combo from Zzounds, and doing the 8 payment installment plan. I can afford $125 every 30 days, and they call it "pay while you play", they ship your gear after the first payment clears. Sort of 'reverse layaway'.
If you have the $$ ready to go, you can probably get a lower price from a Guitar Center, or a scratch and dent thru an online store (Zzounds, American Musical, Sweetwater, etc.) I don't think they do installments for scratch and dent gear, but the price can be wayyyy lower. I am scoping the JTV59 tobacco, it's like $1,500 new on Zzounds. But they are offering some blemished for closer to $1,000; just not with the multi-payment plans... SO be it! Same for GC; they have the JTV59 cherry in stock by me, and it's around $1,000 also, new. But they don't let you take it home until it's all paid for!
Now, the DT25, others with experience can chime in, but its a Bogner tube amp with Line6 interface. It runs as 25w or 12w; though I think it may also have a low volume mode - not sure how that works in terms of what it's actually running into the power amp. Same for some of the Class A, A/B, etc models. If I end up with the JTV, will report back on "bedroom" volumes with the DT25. I live upstairs in a two flat, so I am very limited on how much speaker volume I can make at home...
Combining those three items [JTV + HD500 + DT25, or DT50] is going to give you some overall majorly heady options.. The HD500 can store Variax data, so when you change patches on the HD500 it changes the guitar models and setting on the Variax (when using the ethernet cable), which also powers the JTV while you play. I have read it can take 12 hours to charge the JTV battery up, which could be an issue without that external power source. [NOTE - the connection powers the JTV but does not charge the battery]
In terms of JTV into front jack of a tube amp, endless options. Egnater! As far as JTV+POD HD, or others, into a tube amp, it can be picky. I prefer sending POD to the fx return of my Fender or Marshall amp, and do XLR to the mixer / PA. I did a jam recently, and borrowed the amp that was at the spot. Amazing amp, sounded horrible with the POD though. I had to turn the tone stacks all to zero, and mess with my patches ALOT to get it not sounding really, really bad. I listened back to the direct feed from my POD that got recorded with a line in to a Tascam, and it was 100% not what I heard in the room. That amp was a beautiful old Fender 4x12, amazing amp- it just didn't play nice with the "Full Studio" mode coming off the POD into the front jack. With an FX return, you get some better options - but again, this may all be off topic if you do not intend to use an HD, POD ,etc.