Post Reply - Power Metal Appreciation

Avantasia (the first one) is a v.good album for sure and is interesting enough by merit of the guests alone. 

For a "Keepers + Malmsteen" vision check out Stratovarius. Dreamspace through Visions is a safe bet, they are all very good albums and extremely popular among the fans of the Keepers. If you liked that, you might wanna check out Labyrinth's Return to Heaven Denied, a sort of Italian version of Stratovarius.

The Keepers mark the definitive sound of european power metal. But they are not the only reference. Just like german thrash had Sodom, Destruction and Kreator as the big 3, so did power metal: Rage (I would focus on the Trapped! to End of All Days era, previous might sound too rough for your tastes) and Running Wild, whose Port Royal to Black Hand Inn releases are all STELLAR, albeit kinda repetitive. I would start with Death or Glory. Vocals are not Geoff Tate-ish like Michael Kiske's but they suit the munsic very well and have a huge number of fans.

Another german band whose work has been compared to Helloween's (and rightfully so in terms of quality and they are close enough musically) is Heaven's Gate. Livin' in Hysteria is a classic. 

I would also recommend wholeheartedly Scanner's Ball of the Damned. Amazing power metal album, first song features Ralf Scheepers (of Gamma Ray and Primal Fear fame) on vocals and it is probably among the best power metal songs ever recorded (Puppet on a String).

A few more suggestions:

Lost Horizon - A Flame to the Ground Beneath (check out the 11 minute epic Highlander - vocals steal the show)

Rhapsody - Legendary Tales. Laughable story and concept, dragons and third-rate fantasy stuff but the music is brilliant, a mix of Keeper power/speed with a dose of classical music interludes and sections that gives it a very nice touch of class. The following albums were disappointingly exercises in repetitiveness although the second one has many fans. If you like what you hear, check out also the guitarist's first album Luca Turilli - King of the Nordic Twilight.

Angra should probably get a mention here. More "progressive" than the Keepers for sure although nothing extravagant or "difficult" to follow at all. The first two are your albums. Angels Cry is the straighter of the two but Holy Land has a distinct feeling of its own, blending classical elements and brazilian music. 

For the end, one of my favorite bands, Blind Guardian. Their roots go back to Walls of Jericho instead of the Keepers but they are so talented and so inspired that I fail to see how you won't like them! The albums to look out for are Tales from the Twilight World, Somewhere Far Beyond, Imaginations from the Other Side and Nightfall in Middle-Earth.

Hope this leads to some nice discoveries! To be honest I have the feeling most of this will be already known to you and your question was more rhetoric but perhaps someone else might find something interesting!